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ELEMENTARY CHEMISTRY 



r 



*$ ^ M o *~ v ■ 



AA, carbonating tower. 

b, ammouiacal brine supply. 

d, escape for gas. 

E, pipe through which car- 
bon dioxid is introduced. 

e, sieve to divide stream of 
carbon dioxid. 

G, guide rod for spherical 
diaphragms. 

Q, vacuum tank (connected 
with an air-pump). 

X' , tap for withdrawal of 
precipitated sodium bicar- 
bonate. 

Z, vacuum filter. 




6 



THE SOLVAY CARBONATING TOWEK. 



ELEMENTARY CHEMISTRY 



FOR HIGH SCHOOLS AND ACADEMIES 



j 

BY 

ALBERT L. AREY, C.E. 

ROCHESTER (N.Y.) HIGH SCHOOL 



Nefo fgdtfe 

THE MACMILLAN COMPANY 

LONDON : MACMILLAN & CO., Ltd. 

1899 , 

All rights reserved 






Office o f the 
Register of Cop) 



47542 

Copyright, 1899 
By THE MACMILLAN COMPANY 



SECOND COPY, 



Norfoooti ^rrss 

J. S. dishing ft Co. - Berwick ft Smith 
Norwood Mass. U.S.A. 



9* 



o 



PREFACE 

The course in elementary chemistry herewith presented 
has been in use in the author's laboratories for the past six 
years, and is the result of an effort to increase the useful- 
ness of chemistry as a disciplinary subject. 

The author was long since convinced that the most 
valuable part of the work in chemistry, from an educa- 
tional standpoint, was derived from the processes of thought 
which the student followed when questioned by the teacher 
during his experiment; and the impossiblity of questioning 
each student in a large class individually and thoroughly 
led to the adoption of the plan of adding to the questions 
designed to guide the student's observations which ordinarily 
accompany the directions for experiments, a set of questions 
designed to guide the student's inferences and to suggest a 
definite line of thought in each experiment. This plan 
necessitated the use of the text-book as a laboratory 
manual, to which so many teachers object because of the 
marked resemblance between the notes taken by some 
students and the statements of the same facts in the text- 
book. Under these conditions it was decided to omit all 
reference to those properties of the substances studied in 
the laboratory which can be learned by observation of the 
substances themselves; but to render the work more com- 
plete than it would otherwise be by stating such properties 
as cannot be shown by experiments adapted to secondary 
schools. 

The laboratory thus becomes a study in which the student 
prepares his lesson for the next day by preparing the sub- 



vi PREFACE 

stance assigned and studying its properties, taking complete 
notes as his work proceeds and writing the answers to all 
questions in his note book. The next day's recitation shows 
the character of the student's observations and of his proc- 
ess of thought ; at this time he should be expected to give 
a complete account of the substance studied, including his 
personal observations and inferences ; and the facts stated 
in the text-book concerning its occurrence, preparation, 
properties, and uses. 

The syllabus in chemistry, of the New York State Board 
of Eegents, has been used as a guide in the selection of 
topics for discussion and the order of their arrangement, 
and many of the review questions were taken from the 
Eegents' examination papers. 

In conclusion, I wish to express especial obligation for 
many valuable suggestions to Mr. George M. Turner of the 
Masten Park High School, Buffalo, who has read the entire 
proof. 

A. L. A. 

Rochester, N.Y., 
November, 1899. 



CONTENTS 
PAET I 



PAGE 

Preface v 



Suggestions to the Student 
List of Apparatus 



I. Chemical Action 1 

II. Symbols and Laws 9 

III. Chemistry of the Air 17 

IV. Oxygen 27 

V. Combustion 31 

VI. Nitrogen 39 

VII. Hydrogen 42 

VIII. Chemistry of Water 48 

IX. Problems 64 

X. Compounds of Mtrogen and Hydrogen . . 70 

Ammonia 70 

Ammonium Hydroxid ...... 72 

XL Nitric Acid 76 

XII. Acids, Bases, and Salts 80 

XIII. Compounds of Nitrogen and Oxygen .... 84 

Nitrogen Monoxid . . . . . . .84 

Nitrogen Dioxid .86 

Nitrogen Tetroxid 88 

XIV. The Chlorin Family 90 

Sec. I. Chlorin ' . 90 

II. Hydrochloric Acid 93 

III. Other Compounds of Chlorin ... 97 

IV. Bromin 98 

V. Iodin 100 

VI. Fluorin 102 



Vlll CONTENTS 

CHAPTER PAGE 

XV. Sulfur and its Compounds 107 

Sec. I. Sulfur 107 

" II. Sulfur Dioxid Ill 

" III. Hydrogen Sulfid 114 

" IV. Sulfuric Acid 116 

XVI. Certain Chemical Relations 121 

XVII. The Alkali Metals 130 

Sec I. Potassium and its Compounds . . 130 

" II. Sodium .133 

" III. Ammonium Salts 138 

XVIII. Calcium 141 

XIX. Silver, Copper, and Gold 146 

XX. Zinc and Mercury 150 

XXI. Aluminum 153 

XXII. Iron 157 

XXIII. Tin and Lead 165 

XXIV. Platinum 169 

PAET II 

XXV. Carbon 170 

XXVI. Carbon and Oxygen 181 

Sec. I. Carbon Dioxid ..... 181 

" II. Carbon Monoxid 189 

" III. A Study of Flame .... 192 

XXVII. Hydrocarbons 197 

XXVIII. Destructive Distillation 204 

XXIX. Fermentation 211 

XXX. Phosphorus 220 

XXXI. Arsenic 230 

XXXII. Qualitative Analysis 236 

Preliminary Experiments 236 

Analysis of an Unknown Substance . . . 240 

The First Group 243 

The Second Group 244 

The Third Group 249 

The Fourth Group 256 

The Fifth Group 257 

Acid Tests 258 

Index 261 



SUGGESTIONS TO THE STUDENT 

The subject which, you are now beginning differs from 
those which you have pursued heretofore in several impor- 
tant particulars, and the benefit which you will derive from 
your study will depend, to a large extent, upon your ability 
to adapt yourself to new conditions and requirements. 
Heretofore you have studied statements about things, now 
yon are to study the things themselves; and this change 
affords an opportunity to cultivate your observation. Let 
me urge you to endeavor to see all that there is to see, and 
to be careful that you do not think you see what has no 
existence. 

Heretofore you have depended chiefly upon the author's 
judgment for inferences from facts stated, now you are to 
depend upon your own judgment for inferences from facts 
observed; and this change gives to chemistry its chief 
educational value. Let me urge you to assume a judicial 
attitude, to carefully consider all evidence, that your infer- 
ences may be fully warranted; and to see that your notes 
state only the truth. 

The training of hand and mind which may be acquired 
in the manipulation of chemical apparatus is also of great / 

value, but you must guard against the formation of habits 
of slovenly experimentation. It may sometimes be easier 
to use a piece of apparatus which is "good enough," but 
the satisfaction and the training acquired in arranging the 
perfect apparatus will more than compensate for the extra 
work required. 



L 



APPARATUS 



Each student should he provided with the following apparatus : — 
1 Bunsen burner and tube. 
1 retort stand. 
1 pneumatic trough (1). 

1 16-oz. , wide-mouth, packing bottle. 

2 8-oz., wide-mouth, packing bottles. 

1 two-holed rubber stopper to fit above bottles. 

1 test bottle (2). 

4 pieces of window glass, 2 inches square. 

1 piece of wire gauze, 5 inches square. 

1 piece fine copper gauze, 2\ inches square. 

1 i-inch deflagrating spoon. 

1 test-tube brush. 

1 brush for small tubing. 

1 pair crucible tongs. 

1 funnel, 3 inches in diameter. 

1 test tube, f x 6 inches. 

1 ignition tube, f x 8 inches (3). 

1 250 cc. flask. 

1 rubber stopper to fit flask and ignition tube (4). 

1 evaporating dish, 3 inches in diameter. 

1 flower pot saucer, 4 inches in diameter (5). 

2 pieces rubber tubing, 4 inches long, i hole. 
2 pieces rubber tubing, 4 inches long, \ hole. 
1 piece ^-inch glass tubing, 9 inches long. 

1 piece ^-inch glass tubing, 13 inches long. 

2 pieces ^-inch glass tubing, 9 inches long, with 90° bend 3 inches 

from one end. 

(1) A 4-quart tin pan, or a stoneware milk pan, will answer very 
well for this purpose. 

(2) A 1-ounce morphine bottle, used to test the purity of hydrogen 
and for various other purposes. 

(3) In a number of experiments the 6-inch test tube may be used 
instead of the ignition tube with advantage. 

(4) Short pieces of the several sizes of thick- walled rubber tubing, 
known to the trade as shaft coupling tube, make satisfactory stoppers 
for flasks and ignition tubes. If too small, they may be enlarged by 
slipping over them pieces of larger thin- walled tubing. 

(5) This serves as a support for bottles in the pneumatic trough. 
Any potter will make them with a f hole in the centre and a triangu- 
lar piece cut out of the side. 



PART I 

CHAPTER I 
CHEMICAL ACTION 

1. Elements and Compounds, — The different kinds of 
matter known to man may be divided into two classes : 

(1) Compounds, or those which may be decomposed or 
separated into other substances. 

(2) Elements, or those which have thus far resisted all 
attempts to decompose them. 

About seventy simple substances or elements have been 
discovered, and, so far as is at present known, all com- 
pounds are the result of the chemical union of two or more 
of these. 

It is possible that, as our knowledge of chemistry in- 
creases, many, if not all, of the substances now classed as 
elements may be shown to be compounds. Water was con- 
sidered an element until 1783, and several other so-called ele- 
ments have been resolved into simpler forms since that time. 

There are many chemists who consider the seventy ele- 
ments as so many unsolved problems. 

2. Molecules and Atoms. — The accepted theory of the 
constitution of matter maintains : — 

1. That it is made up of minute particles called mole- 
cules (little masses), each one of which, in a given sub- 
stance, is exactly like its neighbors in weight, volume, and 
structure. 

2. That they move about each other, under the influence 
of heat, as separate bodies. 

B 1 



2 CHEMISTRY 

3. That they are the limit beyond which it is impossible 
to subdivide matter without destroying its identity. 

In accordance with this theory, each molecule of a com- 
pound is believed to contain the same elements that chemi- 
cal analysis shows the large masses of the substance to 
contain, and these smaller portions of the elements are 
called atoms. There is good reason for believing that 
atoms rarely exist in a free state, but that the molecules 
of most elements consist of two or more atoms. 

A molecule is the smallest particle of a substance which can 
exist in the free state, and ichich has the same composition as 
any larger mass of the same substance. 

An atom is the smallest particle, of an element that exists in 
any molecule. 

We may now state the following definitions : — 

A compound is a substance ivhose molecule contains two or 
more kinds of atoms. 

An element is a substance ichose molecule contains only one 
kind of atoms. 

3. The Domain of Chemistry. — Chemistry is that branch 
of science ichich deals with changes in the identity of sub- 
stances; and with the laws, causes, and effects of such changes 

The subject is closely related to physics ; every chemical 
change is accompanied by some physical change, but the 
chemical change differs in one important particular from a 
physical change : the chemical change is due to forces act- 
ing upon atoms, while the physical change depends upon 
forces acting upon the molecule. 

A physical change is one ichich does not destroy the identity 
of the substance acted upon. 



CHEMICAL ACTION 3 

Illustration. When a bar of steel is magnetized it acquires 
a new property, bnt it remains the same substance, and the 
change is physical. 

JL chemical change is one which destroys the identity of the 
substance acted upon. 

Illustration. When a bar of steel rnsts a portion of the 
steel is converted into a new substance which differs from 
the steel in color, tenacity, elasticity, and other properties. 

4. Chemical Action. — In some instances one may be in 
doubt as to whether a chemical change has taken place, and 
in a few instances chemical analysis is necessary to prove it. 
But in general the occurrence of any of the following phe- 
nomena, when two or more substances are mixed, may be 
taken as evidence of chemical action : — 

1. Effervescence. 

2. The evolution of heat and light. 

3. Change of color. 

4. Change of volume. 

5. Change of state. 

6. The development of electricity. 

Exceptions. 1. A change of state by solution of a solid 
or gas. 

2. A change of volume due to the absorption of a gas 
by a solid or liquid, or to a change in temperature. 

Take notes on the following experiments which will be 
performed by the instructor, and designate them as physical 
or chemical changes : — 

Experiment I. — Sugar and potassium chlorate are mixed, and a 
drop of sulfuric acid added. 

Experiment II. — Sulfuric acid is added to syrup. 

Experiment III. — A rubber ruler is electrified. 

Experiment IV. — A beam of sunlight is decomposed with a prism. 



4 CHEMISTRY 

Experiment V. — A piece of platinum wire is heated to redness. 

Experiment VI. — A piece of magnesium wire is heated to redness. 

Experiment VII. — Sulfur and potassium chlorate are mixed in a 
mortar with considerable friction. 

Experiment VIII. — Solutions of potassium iodid and mercuric 
chlorid are mixed. 

Experiment 9 and the succeeding experiments are to 
be performed by the pupil unless special directions to the 
contrary are given. 

Experiment IX. A Chemical Change. — 1. Examine a piece of 
marble carefully, fix its appearance in mind, so that you can detect 
any change. 

2. Drop a small piece in the test bottle and cover it with dilute 
hydrochloric acid. What occurs ? 

3. After a short time test the gas in the upper part of the test 
bottle with a lighted match. Does the match continue to burn ? Is 
the gas combustible ? Is the gas ordinary air ? Why ? Does the 
marble disappear ? 

4. In order to tell whether the marble has been changed chemically, 
the acid must be expelled. To accomplish this, pour the solution into 
an evaporating dish, place it on a piece of wire gauze, and bring the 
liquid to a boil. When the liquid begins to solidify and turn yellow, 
add a few drops of water, repeating, if necessary, to obtain a solid 
white residue. 

Examine this residue, compare it carefully with marble. Set the 
residue aside for 24 hours to determine whether it is permanent when 
L to the air. 



Eill out the following table : — 



Marble 



Residue 



Is it hard or soft ? 

Does it effervesce with hydrochloric acid ? 

Is it soluble in water ? 

Is it permanent in air ? 

How do the properties of the residue compare with those of marble ? 

Is it marble ? 

What have you proven ? 

Experiment X. — Bring together on a flower-pot saucer a little 
phosphorus and iodin. What evidence have you that chemical 
action took place? Have either of the original substances disap- 
peared? Has a new substance been formed? It will be seen that 
simple contact is sufficient to cause the two substances to act upon 
each other. 



CHEMICAL ACTION 5 

Does either substance melt ? "Why ? 

Is this a case of chemical action between solids ? 

Is the action as energetic at first as it is after a few seconds ? 
Explain. 

Caution. — Handle phosphorus with great care ; it takes fire when 
rubbed or cut in the air, and should always be kept in water. 

5. Conservation of Matter. 

Experiment XL — Pour 10 cc. of dilute sulfuric acid into a beaker. 
In a second beaker pour an equal quantity of calcium chlorid solution. 
Place both beakers in one scale pan and balance them carefully with 
weights, sand, or shot, placed in the other scale pan. Now pour the 
calcium chlorid into the sulfuric acid. Does a chemical change occur ? 
Replace the beakers and determine whether the weight of the beakers 
and their contents has been changed. Does chemical action change 
the total quantity of matter in existence ? Was the total quantity of 
sulfuric acid in the world increased or diminished by the above ex- 
periment ? How was the total quantity of calcium chlorid affected ? 
of the white substance formed ? 

6. The Effect of Solution on Chemical Action. 
Experiment XII. — Place as much baking soda as you can take on 

the end of a knife blade in a dry test bottle. Add an equal amount 
of tartaric acid ; shake the bottle to mix the powders thoroughly. 
Has any change occurred ? 

Pour a few cubic centimetres of water into the bottle. What evi- 
dence of chemical action do you observe ? 

Does solution aid chemical action ? Is it because more intimate 
contact of the molecules is obtained when solutions are mixed than is 
possible with solids ? Should diminishing cohesion assist chemical 
action ? State your opinion as to why solution aids chemical action. 

7. Effect of Heat on Chemical Action. 

Experiment XIII. — 1. Mix six grammes of potassium chlorate and 
one gramme of powdered charcoal thoroughly. What occurs ? 

2. Apply a lighted match. Was the change chemical or physical ? 

How does the operation of striking a match illustrate the effect of 
heat upon chemical action ? 

Why do metals rust more rapidly when hot than at lower tempera- 
tures ? Experiment 22 illustrates this effect. Do fuels combine with 
the air when cold ? 



6 CHEMISTRY 

8. Light causes Chemical Action. 
Experiment XIV. — Cut a design from tin-foil and place it on a 

piece of blue print paper. Expose paper and design to sunlight for 
a few minutes. Wash the paper in water. 

Has the sunlight affected the exposed chemical ? In what way ? 

The art of photography is based on the action of light on 
chemicals. In growing plants sunlight causes the decompo- 
sition of carbon dioxid, which is only accomplished by the 
chemist with difficulty. 

In the preparation of hydrochloric acid by synthesis de- 
scribed on page 93, the chemical action is assisted by light. 

Query. — Why do certain colors fade when exposed to light ? 

9. Pressure. — When the two gases, hydrochloric acid 
and hydrogen phosphid, are subjected to increasing press- 
ure they combine to form a crystalline solid known as 
phosphonium chlorid. Similarly sulfur and powdered lead 
may be caused to combine by great pressure, forming lead 
sulfid. 

Query. — What relation does this action suggest between the inten- 
sities of chemical affinity and distances between molecules ? 

10. Concussion or Detonation. — In a very few cases, 
chemical action is brought about by detonation. The 
molecules of the gas acetylene consist of two atoms of 
carbon united with two of hydrogen. If a small quantity 
of mercury fulminate be detonated near a globe filled with 
this gas the carbon is instantly deposited in solid form and 
the hydrogen liberated. This action is not fully under- 
stood; some chemists believe that the particular form of 
sound vibration produced disturbs the motions of the atoms 
constituting the molecule, and thus causes disruption. 

11. Electricity. — If a current of electricity be passed 
through a solution of copper sulfate, the compound is de- 



CHEMICAL ACTION 7 

composed, and many other compounds are affected in the 
same way. In Experiment 40 this effect is also illustrated. 

12. The Effect of Trituration on Chemical Action. 

Experiment XV. — Using pincers, hold a small lump of rosin in the 
Bunsen burner flame, observe the character of the flame produced by 
the burning rosin. Is rosin easily ignited ? Does it burn rapidly ? 
Does the rosin melt before it ignites ? 

Experiment XVI. — Triturate a small piece of rosin in a mortar, 
fill the end of a large glass tube with the powder and blow it into the 
burner flame. Does the finely divided rosin burn with a smoky flame 
or does it flash ? Does it burn as rapidly as in the previous experi- 
ment ? How does the energy of the chemical action compare with 
that observed in the last experiment ? In which case is the higher 
temperature reached ? 

Experiment XVII. — Make a compact pile of about \ cu. cm. of 
powdered rosin on a piece of porcelain or earthenware, ignite with a 
Bunsen burner. How does the chemical action compare with that of 
the previous experiment ? Does the increased chemical action depend 
upon the size of the particles ? Would a solid piece having the same 
area as the sum of the surfaces flash ? Does the chemical activity 
depend upon the surface only ? Upon the mass of the particles only ? 

13. Mechanical Mixture. 

Experiment XVIII. — 1. Mix about four grammes of sulfur and an 
equal weight of fine wrought iron filings on a sheet of paper. Divide 
into three portions. 

2. Examine the first portion with a magnifying glass. Can you 
distinguish the particles of sulfur from those of iron ? Can you 
separate the iron from the sulfur with a magnet ? Now put the mix- 
ture in a test tube and pour water on it. Are the substances combined 
or not ? Shake the tube ; what is the yellow substance floating on 
the water ? Has chemical action taken place ? 

3. Treat the second portion with carbon disulfid. What is the 
black substance at the bottom of the tube ? What has happened ? 
Is the color of the carbon disulfid changed ? What does this indicate ? 
Is a chemical compound formed in this experiment ? 

Experiment XIX. — 1. Put the third portion of the mixture made 
in Experiment 18, in a dry test tube and heat gently. When it is red 
hot remove the tube from the flame. Is there any evidence of com- 
bustion in the tube ? 



8 CHEMISTRY 

2. After the action is over and the tube has cooled down, loosen 
the contents with a short piece of wire, and pour it out on a piece of 
paper. Does the mass look like the mixture of sulfur and iron with 
which you started ? 

3. Examine with a magnifying glass. Can you separate the sulfur 
and iron with water as before ? Can you separate them with a 
magnet ? 

4. Treat a portion of the mass with carbon disulfid. Is the effect 
the same as before ? Is the color of the carbon disulfid changed ? 
What do you conclude concerning the effect of heat on the mixture ? 

REVIEW QUESTIONS 

1. Define chemical action. What assists it ? What retards it ? 

2. Mention those conditions which aid chemical action, («) by 
decreasing the distance between the unlike molecules, (6) by dimin- 
ishing the cohesion of the factors. 

3. Describe an experiment to show that there is no loss of matter 
in chemical change. 

4. Distinguish between a mechanical mixture and a chemical com- 
pound. Illustrate each. 

5. Distinguish between chemistry and physics ; between atoms and 
molecules ; between chemical changes and physical changes. 

6. What mechanical mixture was formed in Experiment 12 ? 
In what part of the experiment were chemical compounds formed ? 

Write answers to these questions in your note-book. 



CHAPTER II 
SYMBOLS AND LAWS 

14. Symbols. — Chemists of all countries have agreed to 
use the initial letter of the Latin name of an element as an 
abbreviation which shall stand for a single atom of that 
element. In case two or more elements begin with the 
same letter the second characteristic letter is added to the 
symbol, thus : — 

C Carbon N Nitrogen ISTa* Sodium 

Ca Calcium S Sulfur K* Potassium 

CI Chlorin Si Silicon Ag Silver 

Some writers use these symbols as mere shorthand signs 
for the full names of the elements. This usage is extremely 
objectionable; students who adopt it will not appreciate 
the important quantitative relations which are shown by 
reactions. 

15. Formulas. — Compounds are represented by a formula 
or a group of symbols, showing the composition of the 
molecule of the substance. 

Thus, the formula of sodium chlorid, ]S"aCl, indicates that 
its molecule contains one atom of sodium and one of chlorin, 
and CaS represents a molecule of calcium sulfid which con- 
tains one atom of calcium and one of sulfur. 

If a molecule contains more than one atom of a given 

* The Latin name of sodium is Natrium, that of potassium is 
folium. 

9 



10 CHEMISTRY 

element, a subnumber is placed a little below and to the 
right of the symbol, and indicates the number of such atoms. 
Thus CaCl 2 is the formula for calcium chlorid, which con- 
tains one atom of calcium and two of chlorin, and the 
formula for ferric oxid, Fe 2 3 , tells us that its molecule 
contains two atoms of iron and three of oxygen. 

If more than one molecule of the substance is to be repre- 
sented, the number is placed before the group of symbols. 
Thus 2Fe 2 3 represents two molecules of ferric oxid con- 
taining four atoms of iron and six of oxygen. 

In the absence of a coefficient a formula always represents 
a single molecule. 

16. The Law of Constant Proportions. — The law of definite 
proportions which has been called the corner stone of modern 
chemistry is as follows : — 

" TJie same compound always contains the same elements 
combined in the same fixed and definite proportions" 

The thousands of analyses which have been made t)f 
various compounds by chemists in all parts of the world, 
and which are now being made every day, are based upon 
this law, and in no single instance have the results obtained 
caused the truth of the law to be questioned. 

17. Combining Weights. — Another important relation is 
to be learned from a study of the composition of various 
substances. Not only is the proportion by weight in which 
a certain element combines with a certain other element, to 
form a given compound, constant, but it is possible to select 
a number for each element, which shall represent the pro- 
portion by weight in which it unites with different elements. 

The composition of the oxids mentioned thus far is given 
below : — 



SYMBOLS AND LAWS 



11 



Mercury, 200 
Oxygen, 16 

Copper, 63.6 
Oxygen, 16 



Lead, 207 
Oxygen, 16 

Zinc, 65.4 

Oxygen, 16 



Iron, 56 
Oxygen, 16 



In each of the above compounds it is observed that there 
are 16 parts by weight of oxygen, and this number or a 
simple multiple of it will express the proportion in which 
oxygen combines with any other element. 

Such numbers have been carefully determined for all ele- 
ments and are called combining weights. 

18. The Law of Multiple Proportions. — The analysis of 
various substances further shows that a given element may 
combine with another in more than one proportion. For 
example, the elements nitrogen and oxygen form several 
compounds having the following composition : — 



Nitrogen 



Nitrous oxid 
Nitric oxid . . 
Nitrous anhydrid 
Nitrogen peroxid 
Nitric anhydrid 



28 parts 
28 parts 
28 parts 
28 parts 
28 parts 



16 parts 
32 parts 
48 parts 
64 parts 
80 parts 



It will be observed that while the quantity of nitrogen is 
the same in all the above compounds the quantity of oxygen 
varies, being twice as great in the second compound as in the 
first, three times as great in the third as in the first, etc. This 
series illustrates the law which applies to all cases in which 
more than one compound is formed from the same elements. 



12 CHEMISTRY 

If tivo elements form more than one compound, the propor- 
tions by weight in which a given element combines with the 
other in each compound will be expressed either by its com- 
bining number or a simple multiple of its combining number. 

19. The Atomic Theory. — The atomic theory was sug- 
gested by John Dalton, an English schoolmaster, early in 
this century, to account for the laws of definite and multiple 
proportions. It maintains — 

1. That with a few possible exceptions all molecules are 
made up of smaller particles. 

2. That these particles are indivisible (they are therefore 
called atoms). 

3. That all atoms of a given element are equal in size and 
weight. 

4. That atoms of different substances have different 
weights. 

5. That the combining weights of the elements are simply 
the relative weights of the atoms, and may therefore be 
called the atomic weights. 

The explanation of the facts of chemistry which this 
theory offers is so satisfactory that it is universally accepted. 

20. Atomic Weights. — As hydrogen enters into combina- 
tion in smaller proportion than any other element, its com- 
bining weight or atomic weight is taken as the unit. When 
we say that the atomic weight of oxygen is 16, we mean 
simply that the atoms of oxygen are sixteen times heavier 
than those of hydrogen. The exact weight of an atom of 
hydrogen has never been determined but it is called a 
microcrith. The atom of oxygen weighs 16 microcriths. 

The following table gives the exact values of the atomic 
weights of the elements referred to in this book. The 
standard is Oxygen = 16. 



SYMBOLS AND LAWS 
Table of Atomic Weights 



13 



Xe-me 


Bym. 


= 16 


Xame 


Bym. 


= 16 


Aluminum . . . 


Al 


27.11 


Antimony . . . 


Sb 


120.42 


Argon . 






A 


(?) 


Arsenic . . . 


As 


75.01 


Barium . 






Ba 


137.43 


Bismuth . . 


Bi 


208.11 


Boron 






B 


10.95 


Bromin .... 


Br 


79.95 


Cadmium 






Cd 


111.95 


Calcium . . . 


Ca 


40.07 


Carbon . 






C 


12.01 


Chromium . 


Cr 


52.14 


Chlorin . 






CI 


35.45 


Copper .... 


Cu 


63.60 


Cobalt . 






Co 


58.93 


Gold 


Au 


197.23 


Fluorin . 






F 


19.06 


Iodin .... 


I 


126.85 


Hydrogen 






H 


1.008 


Lead .... 


Pb 


206.92 


Iron . . 






Fe 


56.02 


Magnesium . . 


Mg 


24.28 


Litliium . 






Li 


7.03 


Mercury . . . 


Hg 


200.00 


Manganese 






Mn 


54.99 


Nitrogen . . . 


N 


14.04 


Nickel . 






Ni 


58.69 


Phosphorus . . 


P 


31.02 


Oxygen . 









16.00 


Potassium . . . 


K 


39.11 


Platinum 






Pt 


194.89 


Silver .... 


Ag 


107.92 


Silicon . 






Si 


28.40 


Strontium . . . 


Sr 


87.61 


Sodium . 






Na 


23.05 


Tin 


Sn 


119.0 


Sulfur . 






S 


32.0 


Zinc 


Zn 


65.41 



21. Reaction. — The force which, is exerted between atoms 
is called chemical affinity, The affinity of a given atom for 
other atoms varies greatly, often being very strong for cer- 
tain kinds of atoms and feeble for others. If,, when any 
substances are mixed, a rearrangement of the atoms would 
produce more stable compounds, i.e. if the force which 
holds the atoms together in the new compounds is stronger 
than that which bound them in their original form, such 
rearrangement will take place. The process of redistribu- 
tion of the atoms in the molecules concerned in the phe- 
nomenon is called chemical action or reaction. 

A reaction is due to chemical affinity and causes a chemical 
change. 



14 CHEMISTRY 

Substances used to bring about desired reactions are 
called reagents. 

The substances which go into a reaction are called factors, 
and those which come from a reaction products. 

Reactions are ordinarily expressed by equations in which 
the symbols and formulae of the factors are placed on the 
left of the sign of equality, and those of the products on 
the right. The algebraic signs plus and minus are used in 
the ordinary sense in the equations. 

The fact that atoms can neither be created nor destroyed, 
even by chemical means, justifies the use of the sign of 
equality to connect factors and products, and it should never 
be placed until the student has " satisfied the reaction," i.e. 
has determined that there are exactly as many atoms of 
each element in the products as there are in the factors. 

Illustration. In Experiment 11 the following reaction 
occurred : — 

CaCl 2 + H 2 S0 4 = CaS0 4 + 2 HC1. 

This should be read as follows : one molecule of calcium 
chlorid plus one molecule of sulfuric acid forms one mole- 
cule of calcium sulfate plus two molecules of hydrochloric 
acid. 

The chemical change occurring in Experiment 19 may be 
expressed as follows : — 

Fe + S = EeS. 

Such equations express very concisely the relations be- 
tween the atoms and molecules in the chemical changes 
which they represent, and every chemical change which is 
clearly understood may be expressed in this way. Equa- 
tions are also useful because of the important quantitative 
relations between masses which are made evident when we 
consider the atomic weights of the elements represented. 



^^" 



SYMBOLS AND LAWS 15 

In the equation given above, the symbol Fe not only signi- 
fies an atom of iron, but it also stands for 56 parts of iron, 
by weight, and the symbol S stands for - 32 parts of sulfur 
by weight. We thus have a mathematical expression which 
shows the relation between the masses of iron and sulfur 
which take part in the chemical change. 

Fe + S = FeS 
56 32 88 

The equation can now be read : — 

56 parts of iron unite with 32 parts of sulfur to form 88 
parts of ferrous sulfid. The solution of many chemical 
problems depends upon this use of equations. (See Chap- 
ter IX.) 

22. Analysis, Synthesis, and Metathesis. — All chemical 
changes may be referred to one of four classes : — 

(a) Compound molecules may be separated into their elements, or 
into simpler groups of elements, as, for example, mercury rust is 
separated into mercury and oxygen in Experiment 25, or as potassium 
chlorate KCIO3, is decomposed in Experiment 30, forming potassium 
chlorid KC1, and oxygen. Such changes are analytic, and the process 
which brings them about is known as analysis. 

(6) Compound molecules may be formed by direct union of ele- 
ments, or simpler groups of elements, as when phosphorus combined 
with iodin, in Experiment 10, forming phosphorous di-iodid PI 2 , or 
when carbon monoxid CO, combines with oxygen to form carbon 
dioxid C0 2 . (See Experiment 101.) Such changes are synthetic, and 
the process is known as synthesis. 

(c) Compound molecules may be formed by a change involving 
both analysis and synthesis, which is known as metathesis, or double 
decomposition. In such processes an exchange of atoms, or groups of 
atoms, takes place between two compound molecules, as when a solu- 
tion of sodium sulfate Na 2 S0 4 , and barium chlorid BaCl 2 , are 
mixed. Each substance is decomposed, and the atoms combine to 
form two new substances, barium sulfate BaS0 4 , and sodium chlorid 
NaCl. 



16 CHEMISTRY 

(d) In some cases new substances are formed without changing 
either the kinds of atoms, or the number of atoms of each kind, in the 
molecule. For example, when a solution of ammonium cyanate 
NH 4 . O . CN, is heated it is transformed into urea N 2 H 4 CO, a substance 
having entirely different chemical and physical properties. It will be 
observed that these molecules contain the same number of atoms of 
each element ; we have excellent evidence, however, that the first one 
contains cyanogen CN, while the second contains carbon monoxid CO. 

REVIEW QUESTIONS 

1. How many atoms of hydrogen in 6 H 2 S0 4 ? of sulfur ? of 
oxygen ? 

2. How many atoms of each element are represented Dy the fol- 
lowing formulae : 2 ZnCl 2 , 3 HN0 3 , 5 H 2 0, 14 NH 3 . 

3. How many molecules of each substance are represented by 
above formula? ? 

4. Define chemical affinity, reaction, reagent, factor, product. 

5. Distinguish between atoms and molecules. Does a chemical 
affinity exist between molecules ? Give a reason for your answer. 

6. What is atomic weight ? How is atomic weight related to 
specific gravity ? 

7. What element is selected as the standard of atomic weight ? 
Why is this element selected ? 

8. State the atomic theory. 

9. State five principles observed in writing chemical symbols and 
formulae. 

10. What is a chemical equation ? What is meant by the combin- 
ing weight of an element ? 

11. State the law of constant proportions. Of multiple proportions. 

12. State five principles to be observed in writing chemical 
equations. 



CHAPTER III 
CHEMISTRY OF THE AIR 

23. The Formation of Rust. 

Experiment XX. — 1. In a small porcelain crncible or a clay pipe 
bowl put a small piece of lead or zinc. Heat with laboratory burner 
and notice the changes that take place. Do not allow the containing 
vessel to become too hot, for liquefied rust will be absorbed. After the 
lead begins to melt, stir with a thick iron wire. Observe carefully 
what forms on the surface of the metal. Does the lead retain its bright 
mirror-like surface if not stirred ? Continue to heat and stir until the 
substance is changed to a powder. What is its appearance now ? 

2. Let it cool. Is it lead ? What difference is there between the 
action in this case and in melting ice and cooling the water again ? 
Which is chemical and which is physical action ? Why ? Was the 
change just observed produced by the heat or by the action of the air ? 
In order to answer this question let us repeat the experiment, prevent- 
ing any action of the air by covering the metal with a film of melted 
rosin. 

Experiment XXL — Repeat Experiment 20, adding as much 
powdered rosin as can be lifted on the blade of a penknife. Do 
not stir the metal. Does it rust or does the surface remain bright and 
mirror-like ? Is it changed to powder ? How do you explain the 
difference in result of this experiment and the last ? What do you 
conclude concerning the cause of the change produced in the previous 
experiment ? Is the action due to the high temperature or to the 
action of the air or to both ? Does lead rust more rapidly at high than 
at low temperature ? Eosin is used to prevent rusting of hot metals 
in process of soldering. 

24. Effects of Air on Iron at Ordinary and at High Tempera- 
tures. 

Experiment XXII. — Wind a piece of No. 30 iron wire about a foot 

long around the finger and heat the loops thus formed in the tip of a 

laboratory burner flame for a minute or two. Holding the loop over 

a sheet of paper, straighten the wire. Compare the scale which drops 

c 17 



18 CHEMISTRY 

off with the rust formed on iron at ordinary temperatures. Is it the 
same color ? Does iron rust more rapidly at high or low tempera- 
tures ? How do you know ? Has a chemical change occurred ? Pass 
a magnet over a mass of red rust ; of black rust. Are they magnetic ? 
(See paragraph on Oxids in Nature, page 37.) 

25. Various Ways of Protecting Iron. 

Several years ago Professor Barff, of London, suggested 
that iron might be protected from the action of the air by 
exposing it to superheated steam at high temperature, thus 
forming a coating of black rust on its surface. The pro- 
cess has been somewhat modified, and is now known as the 
Bower-Barff process. It is quite extensively employed as 
a finish for iron ornaments, and has been used in certain 
cities to protect water pipes. 

Zinc and lead are protected from the action of the air by 
the coating of oxid which forms on their surface. 

Queries. — Mention several ways of protecting iron from the action 
of the air. Why do we blacken stoves ? Why are some parts nickel 
plated ? What is galvanized iron ? What is a tin pan made of ? In 
what two ways are water pipes protected ? How are iron bridges pro- 
tected ? Bicycle frames ? 

26. Does the Weight of a Metal change when it rusts ? 
When a chemical change occurs it is due to the addition 

of some element or elements to the substance changed, or 
to the extraction of some element or elements from the sub- 
stance changed. Now, since loss or gain in matter means 
loss or gain in weight, let us determine whether a sub- 
stance was added to or driven off from the iron in the last 
experiment. 

Experiment XXIII. (Performed by the instructor.) — Weigh a 
piece of No. 30 wire, heat as in the last experiment ; when cool weigh 
again. Explain. 

Does heating in contact with air drive something away from the 
iron or cause something to combine with it ? From what source is 
the substance derived ? 



CHEMISTRY OF THE AIR 19 

27. The Material which combines with the Metal to form 
Rust. 

We now desire to know the nature of the substance which 
causes metals to rust ; and as it can be expelled easily from 
the rust which forms on mercury, we shall study that sub- 
stance. As air is an invisible gas, special precautions must 
be taken to prevent its loss or mixture with other substances. 

Experiment XXTV. A Method of Collecting Gases. — Fill the 
yellow dish (see description of apparatus, p. xi) one-third full of 
water. Place the flower-pot saucer bottom side up in the water. 
Fill one of the medium sized bottles with water, cover with a glass 
plate, and invert on the flower-pot saucer ; remove the glass plate. 
If your work has been carefully performed your bottle will be full of 
water. (If not, try again.) 

Now put the end of a glass tube at the opening at the side of the 
flower-pot saucer and blow gently through it. What do you notice ? 
"What is in the bottle after the water is out of it ? Where does it 
come from ? 

This method of collecting gases over water may be used for all 
gases not dissolved by water. 

Students should attempt to devise other methods. Could a rubber 
bag be used ? What advantage has the method used in this experi- 
ment over other methods ? 

Experiment XXV. A Study of Mercury Bust. — 1. Weigh accu- 
rately a small glass tube, closed at one end, containing about a 
gramme of mercury rust. 

2. Holding the tube in a nearly horizontal position with a pair of 
crucible tongs, heat the red powder strongly for some minutes, or until 
a bright mirror-like deposit appears near the open end of the tube. 

3. Weigh the tube again. Is there any evidence that an invisible 
substance has escaped ? After weighing the tube, examine the de- 
posit near the open end. Scrape some of it from the tube with an 
iron wire ; what is it ? What have you learned about the constitu- 
ents of mercury rust ? Is either constituent a solid ? a liquid ? a gas ? 

4. Arrange an ignition tube, as shown in Fig. 1, so that any gas 
generated in the tube may be collected in the bottle. Fill the bottle 
with water. 

5. Put about 15 grammes of mercury rust in the ignition tube and 
apply heat. Describe the gas collected. 



20 



CHEMISTRY 



6. Test with a glowing match stick. Remove the match and put 
it back a few times. Is there any difference between the burning in 
the bottle and out of it ? Is the gas air ? Has the gas which formed 
the rust a marked ability to make things burn ? Has the color of the 
mercury rust changed ? 




7. Remove the ignition tube and pour its contents on a piece of 
paper. How is the color affected ? Compare it with some of the 
mercury rust which has not been heated. What effect has the air 
had upon the hot rust from the tube ? Has the air entirely restored 
the gas driven off by the heat ? Is the gas collected in this experi- 
ment pure air, or a part of the air ? 

The chemical change which occurs in this experiment may be ex- 
pressed as follows : — jjgO = Hg + 0. 

The gas which causes metals to rust is called oxygen^ its 
compounds are called oxids, and the process of forming oxidfl 
is known as oxidation. The rust formed on iron at ordinary 
temperatures is called ferric hydroxid. That formed at high 
temperatures is ferrous oxid and ferric oxid, probably in 
chemical combination. It is called magnetic oxid. 

We have observed that oxygen makes things burn vigor- 
ously, and, although it is deemed best to reserve the dis- 
cussion of combustion for a subsequent chapter, the next 
two experiments are given here to show the relation between 
the processes of rusting and burning. 



CHEMISTRY OF THE AIR 21 

28. Effect of excluding the Air from a Flame. 

Experiment XXVI. — Close the holes at the bottom of your labora- 
tory burner. How is the character of the flame affected ? Explain. 
Why do we close the stove dampers at night ? "What is the effect of 
removing the ashes and clinker from a stove ? Why ? 

Suggestion. — Wrap a piece of cloth around the lower part of a 
kerosene lamp burner, covering the holes through which the air enters 
the chimney. How does this affect the flame ? What has air to do 
with the combustion of oil ? How does a lamp chimney increase the 
brightness of the lamp name ? How does a fire extinguisher put out 
a fire ? It is possible that burning, like rusting, is simply a chemical 
union of air, or a part of the air, with the fuel. Let us determine 
whether this is so by the method used in Experiment 23. 

29. Comparison of the Weight of the Products of a Burning 
Candle with the Amount lost by the Candle. 

Experiment XXVII. (Performed by the instructor.) — On one side of 
a delicate balance, apparatus which will absorb the products of combus- 
tion is suspended over a candle, the whole being exactly balanced with 
weights on the other side of the balance. The candle is righted and 
the gases are drawn into the absorbing apparatus. As the candle 
burns away the side of the balance carrying the apparatus grows 
heavier. The weight of the products is greater than the loss of weight 
of the candle. 

Is the candle converted into heat ? Is heat matter ? Where does 
the matter causing the increase come from ? Does this prove that the 
candle is indestructible ? What is your conclusion concerning the 
nature of combustion ? 

30. Analysis of the Air. — We have learned that oxygen 
is a part of the air, and now desire to learn what proportion 
of the air is oxygen. 

Experiment XXVIII To determine the per cent of oxygen in the 
air. Cooley-s method. Apparatus required. — A small glass funnel. 
A six-inch test tube, with a two-holed rubber stopper to fit same. 
Rubber bands, a measuring glass, 155 cc. of the absorbent liquid. A 
piece of glass tubing two inches long fitted in one of the holes of the 
stopper, a piece of glass rod the same length in the other hole, and a 
piece of thin rubber tubing six inches long, in which a piece of glass 



22 



CHEMISTRY 




rod half an inch long and of such size as to prevent a liquid from 
running through the tube, is placed. 

Manipulation. — 1. Arrange the apparatus as shown in Fig. 2. 

2. In your test bottle dissolve a small teaspoonful 
of pyrogallic acid in 10 cc. of water, quickly add 
5 cc. of a strong solution of sodium hydroxid, and 
pour into the funnel. This liquid absorbs oxygen 
and carbon dioxid rapidly. 

3. Holding the test bottle under the rubber cork, 
pinch the rubber tube where the glass rod closes it 
until a little of the liquid runs through the tube. 
Carefully remove the drop which is suspended from 
the glass tube with a piece of filter paper. 

4. Now remove the glass rod from the hole in the 
rubber stopper and put the test tube on the stopper ; 
allow it to hang there a minute or two to allow the 
heat communicated to the tube and air which it con- 
tains to pass away. Then insert the glass rod in the open hole in the 
stopper. We have now isolated a definite volume of air at the same 
temperature and pressure as the air of the room, and during the ab- 
sorption and the measurements care must be taken to prevent change 
in the volume under analysis, either by the escape of a portion or by 
the introduction of more air from without. 

5. Pinch the rubber tube at the glass rod to allow some of the ab- 
sorbent liquid to run down into the test tube ; a little stream runs in 

at first, then drops follow each other more and 
more slowly ; when these have nearly ceased 
allow the apparatus to stand for two or three 
minutes. Then allow more of the absorbent 
liquid to enter the test tube. Repeat the opera- 
tion every two minutes until only a drop or two 
enters the tube when opened. 

6. The gas in the test tube is now compressed 
by the weight of the liquid in the rubber tube ; 
before measurements can be made the pressure 
must be adjusted to that of the air in the room. 
This is accomplished by grasping the test tube 
by the flange (so as not to warm the gas), rais- 
ing the tube as shown in Fig. 3, and pinching 
the rubber tube to open a passage between the 
two masses of liquid. Keep this passage open and move the test tube 
up or down until the liquid stands at the same level in the test tube 




CHEMISTRY OF THE AIR 23 

and the funnel ; then close the passage between them. Your results 
will depend to a great extent upon the care with which this adjust- 
ment is made. 

7. Slip a rubber band around the test tube so that its upper edge 
marks the position of the bottom of the stopper. 

8. Remove the test tube from the apparatus and pour the absorbent 
liquid into a measuring glass. This represents the volume of gas 
absorbed ; record the number of cubic centimetres. 

9. Now fill the test tube with water to the top of the rubber band 
and measure this volume. This represents the volume of air analyzed. 

We have thus determined, the number of cubic centi- 
metres of oxygen in a certain number of cubic centimetres 
of air, from which we may determine the number of cubic 
centimetres of oxygen in 100 cc. of air ; i.e. the percentage 
of oxygen in air. 

31. Other Substances in the Air. — When a gas called 
carbon dioxid is passed through lime water the latter be- 
comes cloudy because a white solid (a precipitate) is formed. 
This is the test for carbon dioxid. 

Experiment XXIX. — 1. Take 20 or 30 cc. of lime water in your 
test bottle. Blow through a glass tube in such a way that the exhaled 
air bubbles through the lime water. Does the lime water become 
cloudy or does it remain clear ? What does this experiment prove 
regarding air exhaled from the lungs ? 

2. Force air from a bellows through lime water. What inference 
do you draw from this experiment ? 

Carbon dioxid was absorbed with the oxygen in Experi- 
ment 28, but the amount is so small (about ^ of one per 
cent) that it may be disregarded. 

Does water vapor exist in the air ? To answer this ques- 
tion, think of the moisture which collects on the outside of 
an ice pitcher in summer. What is dew ? What is frost ? 

The gas which remains in the apparatus after absorbing the 
oxygen and carbon dioxid (Experiments 28 and 31) is nearly 
pure nitrogen. Nitrogen is fully discussed in Chapter VI. 



24 CHEMISTRY 

ARGON 
Symbol A. — Atomic Weight 19.9 

32. Some years ago Lord Rayleigh proved that nitrogen 
obtained by removing the oxygen from the air was invariably 
denser than that obtained from chemical compounds. He 
undertook to determine the cause of this difference, and in 
conjunction with Professor Ramsay found that this greater 
density was due to the presence of an unknown gas, which 
they succeeded in isolating and to which they gave the name 
Argon. Their discovery was announced January 27, 1895. 

Argon is a gas forming -^ part of the air ; it is also 
found among the occluded* gases in some specimens 
of meteoric iron. As indicated by its name, argon is the 
most inert element ; it has thus far resisted all attempts 
to get it to combine with other elements. Its chief char- 
acteristic, therefore, is its "glorious uselessness." It is 
sparingly soluble in water, boils at — 187° C. and freezes at 
- 189° C. 

Since the discovery of argon several other new elements 
have been found in the air, with properties quite similar to 
those of argon. 

33. Air as a Mixture. — Air is believed to be a mechanical 
mixture of nitrogen and oxygen, and not a chemical com- 
pound, for the following reasons : — 

1. Air contains approximately 79 % of nitrogen and 21 % 
of oxygen. This is not in accordance with the law of 
multiple proportions. 

2. If nitrogen and oxygen be mixed in the above propor- 
tions the mixture possesses all the properties of air, but is 
not accompanied by any phenomena which indicate chemi- 

* Define term. 



CHEMISTRY OF THE AIR 25 

cal action. Whenever chemical union takes place, there is 
some change in the temperature of the substance; when 
nitrogen and oxygen are mixed as above described there is 
no change in the temperature. 

3. The law of definite proportion states that the compo- 
sition of a given chemical substance is invariable; that of 
air varies slightly. 

4. Air is somewhat soluble in water, but each gas is 
dissolved independently. 

If we shake up air and water in a bottle some of the air 
will be dissolved; if we boil this saturated water the air 
which escapes can be collected and analyzed. This has 
often been done, and it has been found to contain a larger 
proportion of oxygen than the original atmospheric air. 



Thus 


Atmospheric 


Dissolved 


N 


79.04 


66.36 





20.96 


33.64 



This change in the proportion could not occur if the air 
was a compound, for a compound is dissolved as a whole. 
The above numbers exactly agree with the solubilities of 
oxygen and nitrogen separately. 

REVIEW QUESTIONS 

1. Describe the effects of the partial and of the total exclusion of 
air from a flame. 

2. State how the effect of air on iron at high temperatures differs 
from the effect of air on iron at ordinary temperatures. 

3. Describe a chemical method of protecting iron from the action 
of the air. 

4. How does the weight of the products of the combustion com- 
pare with the amount lost by the candle ? Why ? 

5. Does the weight of the scale which flies from the blacksmith's 
hot iron equal the weight lost by the iron ? Why ? 

6. Has air a chemical formula ? 



I 



26 CHEMISTRY 

7. Is the air a mixture or a compound ? Describe an experiment 
to prove the correctness of your answer. Give reasons for your 
answer. 

8. Describe the Bower-Barff process of protecting iron. 

9. Give an account of the discovery of argon. State the prop- 
erties of argon and its occurrence in nature. 

10. Explain the effect of excluding air from a flame. Mention 
some practical appliance whose efficiency depends on the principle 
involved. 

11. What is the scale which accumulates about the blacksmith's 
anvil? 



CHAPTER IV 
OXYGEN 

Symbol O. — Atomic Weight 16 

34. Occurrence. — Oxygen is the most abundant of all the 
elements, comprising by weight A of the air, -| of the water, 
| of all the animal bodies, and about -J of the crust of the 
earth. 

The word oxygen means " acid-former," but it is a mis- 
nomer. Chemists supposed that it was present in all acids 
when the name was given. 

35. Preparation. — Oxygen may be easily obtained by 
heating potassium chlorate. 

Cautiox. — The following precautions must be observed : — 

1. The chemicals must be free from impurities which might cause 
an explosion. If a small quantity of the mixture when heated in a 
dry test tube melts quietly, the mixture may be considered safe. 

2. The ignition tube must be inclined. 

8. It must not be more than one-third full. 

4. The upper part of the mixture in the tube should be heated first. 

5. The heat must be so regulated that an even and not too rapid 
flow of the gas may be secured. It may be necessary to withdraw 
the flame and replace it when the gas slackens. 

Experiment XXX (Two students will work together.) — 1. Arrange 
the apparatus as in Experiment 25. Mix equal weights of manganese 
dioxid and potassium chlorate, and heat about ten grammes of the 
mixture in a test tube. Collect four bottles of the gas evolved over 
water. 

2. Place the bottles on the table, mouth upwards, covering them 
with a glass plate. What is the color of the gas ? Odor ? Taste ? 
Is it soluble in water ? The slight cloud which appears in the bottle 
27 



28 CHEMISTRY 

at first is due to a substance which is not oxygen. After a while this 
disappears and oxygen remains. 

3. Drop a piece of charcoal, obtained by charring the end of a 
match stick, in the first bottle. In another lower a deflagrating spoon 
containing a little sulfur. 

4. In the third drop a piece of phosphorus about the size of a 
pea. (Care !) Let them stand quietly and observe what changes, if 
any, take place. Does oxygen at ordinary temperatures act readily 
on these substances ? 

•"). Now thrust a piece of red-hot charcoal (a glowing match stick) 
into the first bottle. Note difference in action. 

6. Remove the deflagrating spoon from the second bottle ; set fire 
to the sulfur. Notice whether it burns with ease or with difficulty. 
Does the sulfur burn more readily in the oxygen than in the air ? 

7. Remove the phosphorus from the third bottle ; place it in the 
deflagrating spoon, ignite, and quickly lower it into the bottle again. 
Describe the action. How does the action of oxygen on these sub- 
stances at high temperatures compare with the action on the same 
substances when cold ? Does either substance burn as vigorously in 
air ^s in oxygen ? 

Reaction : 2 KC10 3 + MnO a = 2 KC1 + Mn0 2 + 3 Og. 

The Test for Oxygen. — Thrust a glowing splinter of wood into one 
of the bottles. What occurs ? 

Note. —No substance but oxygen can cause a spark to burst into 
flame. How can you determine whether a bottle contains oxygen or 
not? 

36. Physical Properties. — Pure oxygen is colorless, odor- 
less, and tasteless; it is heavier than air. What are its 
other physical properties? It is only sparingly soluble, 
water dissolving only 3% of it. Oxygen may be liquefied 
at —118° C. by a pressure of fifty atmospheres. The liquid 
has a pale steel-blue color, and boils at —181° C. under 
ordinary pressure. 

37. Chemical Properties. — Oxygen combines with every 
known substance except fluorin, and is characterized by 
great chemical activity. It is the great supporter of com- 



OXYGEN 29 

bustion. If both the oxygen and a combustible substance 
be absolutely dry, it has been shown that they will not 
combine. No satisfactory explanation of this fact has 
been offered. Oxygen is the only element capable of sup- 
porting respiration. Fish breathe the dissolved oxygen in 
water. 

38. Uses. — Oxygen is necessary to animal respiration, 
to ordinary combustion, fermentation, and decay. It is 
used in the arts to increase the intensity of combustion, 
and is also used in medicine. 

39. Burning in Air. 

Experiment XXXI. — 1. Pour 10 cc. of lime water into a bottle 
containing air, shake the bottle, note the effect on the lime water ; now, 
nsing a short piece of wire as a handle, lower a burning match into 
the bottle ; when it has gone out cover with the hand and shake the 
bottle ; note the changed appearance of the lime water. A milky- 
appearance proves the presence of carbon dioxid. 

2. Repeat the experiment using a bottle of oxygen. 

When sulfur burns in air a gas having the characteristic odor of 
burning matches is formed. 

3. Determine whether the gas formed when sulfur is burned in 
oxygen is the same that is formed when it burns in air, by burning 
sulfur in a bottle containing air and in one containing oxygen, and 
compare the odors of the gases formed. Discuss the relation between 
combustion in air and in oxygen. 

The difference in activity is due entirely to the fact that 
in air oxygen is diluted with another gas which does not 
support combustion. 

REVIEW QUESTIONS 

1. Describe the preparation of oxygen from potassium chlorate. 
Mention precautions to be observed. 

2. What is the office of manganese dioxid in the above process ? 

3. What are the tests for oxygen ? 



30 CHEMISTRY 

4. Compare the action of oxygen on charcoal at ordinary tem- 
peratures with its action at high temperatures. 

5. Compare the product obtained by burning charcoal in oxygen 
with the product obtained by burning it in air. 

6. Compare the action of oxygen on phosphorus at ordinary tem- 
peratures with its action at high temperatures. 

7. What can you say of the products of combustion in air and in 
oxygen ? 

8. Discuss the occurrence of oxygen in nature. 

9. State the physical properties of oxygen ; the chemical prop- 
erties. 

10. Does oxygen occur uncombined in nature ? 

11. Mention several compounds containing oxygen which occur 
in nature. 

12. Does oxygen display greater energy at high temperatures than 
at low temperatures ? 



CHAPTER V 
COMBUSTION 

40. Ordinary Combustion. — In its broadest sense, the term 
combustion is applied to all cases of chemical action which 
are accompanied by an evolution of heat and light. In the 
majority of cases, however, oxygen is one of the elements 
concerned in combustion, and because of the rarity of the 
exceptions, the term is sometimes defined as the union of a 
substance with oxygen, accompanied by the evolution of 
heat and light ; and the classification of substances as com- 
bustible and incombustible depends upon this definition of 
the term. Thus a combustible substance is one which unites 
with oxygen with evolution of light and heat, and an 
incombustible substance is one which cannot unite with 
oxygen. 

Many substances are products of combustion ; thus water 
is composed of hydrogen and oxygen, and carbon dioxid of 
carbon and oxygen. In these compounds the hydrogen and 
the carbon have already combined with oxygen, and cannot 
directly combine with more. 

41. Kindling Temperature. — A wise provision of nature 
makes it necessary to raise the temperature of substances 
slightly above that which ordinarily obtains, to cause them 
to combine rapidly with oxygen. If this were not true we 
should have no fuels. Substances differ widely in the tem- 
perature to which they must be raised to cause them to 
combine with oxygen, but for each combustible substance 

31 



32 CHEMISTRY 

there is a definite temperature at which it combines with 
oxygen with sufficient energy to develop heat and light, and 
this is called the kindling temperature. 

If the kindling temperature of a substance is below the 
ordinary temperature, it will take fire when it comes in 
contact with the air, and must, therefore, be kept out of 
contact with the air. Such substances are said to be spon- 
taneously inflammable. Several substances have kindling 
temperatures below a red heat, e.g. the gaseous hydrogen 
phosphid may be ignited with a test tube containing boiling 
water, and the vapor of carbon disulfid may be ignited with 
a glass rod heated to 120°. Most solid fuels require a tem- 
perature slightly above redness, while the diamond must be 
raised to nearly a white heat before combustion begins. In 
starting a fire we take advantage of differences in the 
kindling temperatures of substances. For example, paper 
is easily ignited, but the heat which it develops cannot 
ignite the anthracite ; hence we often put charcoal between 
the paper and the coal, as paper can ignite the charcoal. 
The use of a coating of sulfur or paraffin on matches, to 
enable the phosphorus to ignite the wood, is another in- 
stance of the use of a substance having an intermediate 
kindling temperature. 

The temperature produced by the combustion of a sub- 
stance is not necessarily the same as its kindling tempera- 
ture. In all cases of ordinary combustion the temperature 
produced is higher than the kindling temperature of the 
substance; burning particles thus raise adjoining particles 
to the kindling temperature, and the burning continues 
without further application of heat when once started. 

There are, however, numbers of cases in which the com- 
bustion cannot proceed without the continuous application 
of heat. The heat of the electric spark ignites nitrogen, 



COMBUSTION 33 

but the heat developed does not kindle the adjacent par- 
ticles. 

The facility with which a combustible substance may be 
ignited depends upon the quantity of heat, i.e. upon the 
number of heat units required to raise it to its kindling 
temperature. But, as we learn in physics, the temperature 
to which a substance is to be raised is only one of four 
quantities which determine the number of heat units re- 
quired ; the other three being the specific heat of the sub- 
stances, its mass, and the number of heat units lost by 
conduction and radiation. 

The amount of carbon to be kindled in a given stove 
depends upon the specific gravity and the porosity of the 
fuel; for example, charcoal, gas coke and anthracite coal 
are each of them nearly pure carbon, but they require very 
different amounts of kindling to ignite them. The specific 
gravity of the solid portions of these fuels are as follows : — 

Pine charcoal 40 

Gas coke 86 

Anthracite 1.60 

while the cell space or porosity expressed in cubic centi- 
metres in 100 grammes of the fuel is as follows : — 

Pine charcoal 200.4 

Gas coke 60. 

Anthracite 3.6 

We thus see why charcoal requires comparatively little 
kindling to ignite it, although its kindling temperature is 
the same as the others. 

The amount of heat lost by conduction has an important 
bearing on the amount of kindling required to build a fire. 
If the fuel is a good conductor of heat, it will be diffused 
throughout the mass, and such fuels are more readily 



34 CHEMISTRY 

ignited if they are in small pieces, e.g. shavings are easier 
to ignite than a block of the same kind of wood. 

Experiment XXXII. — Hold the laboratory burner horizontally 
over a sheet of white paper. Sprinkle some fine iron filings through 
the flame. What occurs ? Pick up a few of the larger pieces on the 
paper and drop them througli the flame again. What particles are 
raised to incandescence ? Why ? 

Masses of metal in contact with the fuel often occasion 
considerable loss of heat by conduction. This action is 
nicely illustrated in the following experiment. 

Experiment XXXIII. — Light a candle, bring a piece of wire gauze 
slowly down on the flame until it touches the wick. What occurs ? 
Note the conditions above and below the gauze. Hold a lighted match 
above the gauze. What occurs ? Explain. To what extent is the gauze 
heated ? The Davy safety lamp used by miners illustrates this action. 

42. Heat of Combustion. — It must be clearly understood 
that the light produced by combustion is due to the fact 
that the chemical action develops heat more rapidly than it 
can escape, thus raising the body to incandescence. There 
are many cases of oxidation, however, which take place 
slowly, or in which the substance is so situated that the 
heat is conducted away as fast as developed and in which a 
high temperature is not reached. The most important illus- 
tration of this action is the oxidation occurring within our 
bodies, which supplies the heat necessary to our existence. 
Other illustrations are found in the heat developed in com- 
post heaps, in hotbeds, in the decay of wood, in cases of 
" spontaneous combustion," and in the rusting of iron. 

The higher temperature acquired by a substance when it 
burns is readily accounted for by the difference in the rate 
at which it combines with oxygen. When two substances, 
such as carbon and oxygen, combine, their chemical affinity 
causes the atoms to rush toward each other, and the col- 



COMBUSTION 35 

lision which, ensues increases their rate of vibration; that 
is to say, it develops heat. The amount of heat developed 
by the collision which forms a single molecule depends upon 
the magnitude of the attractive force and not upon the rate 
at which similar molecules are formed ; it follows, there- 
fore, that the oxidation of a given mass of a substance will 
develop exactly the same amount of heat when it burns that 
would have been developed if it had been oxidized slowly. 

43. Chemical Energy. — All cases of direct chemical com- 
bination are due to attractions between unlike atoms; and 
whether the attraction be great or small, the collison of the 
atoms will develop heat. When molecules consisting of more 
than one atom act upon each other, the force which holds 
the atoms together in the original molecules must be over- 
come before a chemical change can occur; and the amount of 
heat developed in any reaction will accordingly depend upon 
the magnitude of the attractions of the atoms of the factors, 
as compared with the value of the attractions of atoms of 
the products. If the latter exceed the former, a chemical 
change will occur, accompanied by an evolution of heat. 
Chemical changes which evolve heat are known as ex- 
othermic changes, and those compounds which are formed 
from their elements by such changes are known as ex- 
' otliermic substances. Such substances are very stable, and 
when they are separated into their original elements the 
same quantity of heat that was evolved when they were 
formed disappears, or more exactly, is transformed into 
chemical potential energy. The formation of a much 
smaller class of substances is accompanied by the dis- 
appearance of heat; these are known as endothermic 
bodies, and when they are decomposed heat is evolved. 
They are usually unstable and often very explosive. All 



36 CHEMISTRY 

endothermic substances possess chemical energy and can do 
work ; that is to say, a substance which can combine with 
other substances without the aid of external energy possesses 
chemical energy. Much of the mechanical energy of the 
world is derived from endothermic substances, e.g. the fuels. 
The decomposition of carbon dioxid in the plant is an 
endothermic reaction in which the energy of the sunlight 
disappears. The carbon thus formed is stored up and may 
be again oxidized. For this reason the energy derived from 
wood and coal is sometimes spoken of as " stored sunlight." 

44. Nomenclature of the Oxids. — The simplest chemical 
compounds are those composed of two elements only ; they 
are known as binary compounds. Many binary compounds 
end with the letters id; but this rule cannot be depended 
upon in all instances. 

Binary compounds of oxygen are called oxids ; they are 
very numerous ; e.g. oxygen forms five distinct compounds 
with nitrogen. 

When there are two oxids of the same element it is quite 
common to distinguish them by adding the suffix ic to the 
name of the element to denote the oxid having the greater 
amount of oxygen, and the suffix ous to the name of the 
element to denote the oxid having the smaller proportion of 
oxygen. Thus, mercuric oxid has a larger percentage of 
oxygen than mercurous oxid, and nitric oxid a larger per- 
centage than nitrous oxid. 

If there are more than two oxids of the same element, 
prefixes are often used. Thus a peroxid contains a larger 
percentage of oxygen than the oxid to which the suffix ic is 
applied. Nitrogen peroxid, which contains a larger propor- 
tion of oxygen than nitric oxid, illustrates this usage. 

A more scientific and simpler method of naming oxids 



COMBUSTION 37 

has been suggested, and is quite generally used. Accord- 
ing to this plan the first part of the name of the oxid con- 
sists of the name of the element oxidized, and the second 
part of the name indicates the number of atoms of oxygen 
which the oxid contains, by the use of certain prefixes de- 
rived from the Greek. Oxids containing one atom of 
oxygen are called monoxids, e.g. carbon monoxid; those 
containing two atoms dioxids, e.g. carbon dioxid ; those con- 
taining three atoms, trioxids, e.g. sulfur trioxid, etc. 

45. Oxids in Nature. — Water, or hydric oxid is the most 
abundant oxid in nature, and sand (silicon dioxid) is next. 

The ores of some of the most important metals are oxids, 
e.g. the red iron ore so common in this country is a com- 
pound of iron and oxygen, the molecule of which contains 
two atoms of iron and three of oxygen ; and black iron ore, 
or lode stone, contains three atoms of iron and four of 
oxygen in its molecule. Many other ores are oxids, e.g. 
those of tin, manganese, etc. 

REVIEW QUESTIONS 

1. How do substances formed by burning in air compare with 
those formed by burning in oxygen ? 

2. Why is not combustion as rapid in air as in oxygen ? 

3. Define combustion. What are combustible substances ? 

4. Define kindling temperature. Which has the highest kindling 
temperature, sulfur, carbon, or phosphorus ? 

5. Mention examples of slow oxidation. How does slow oxida- 
tion differ from combustion ? 

6. Compare the amount of heat given off during slow oxidation 
and combustion. 

7. What is meant by chemical energy ? What substances possess 
it ? What substances do not possess it ? 

8. From what source is the mechanical energy of wood derived ? 
Explain. 

9. What are oxids and how are they named ? What do the ter- 
minations " ic " and " ous " indicate? 



38 CHEMISTRY 

10. What important oxids occur in nature ? Why are they so 
abundant ? 

11. Give evidences that a part of the air combines with the fuel in 
combustion. 

12. Describe an experiment to show the relation of the weight of 
the products of a burning candle to the weight of the portion of the 
candle consumed. 

13. How is combustion related to or distinguished from chemical 
action in general ? 

14. Mention conditions that favor combustion and chemical action 
in general. 

15. Mention a condition favoring some chemical action but not 
combustion. 

16. What is meant by kindling temperature ? Explain the theory 
of shaving wood for use in starting a fire of the same kind of wood. 

17. How does the chemical energy of the combustion of hydrogen 
compare with that of the combustion of other elements ? Why ? 

18. Why is a fire of seasoned wood hotter than a fire of green 
wood ? 

19. Explain the use of sulfur in making the common friction 
match. 

20. Why is a wood fire easily started with wood shavings ? 

21. Upon what does the temperature reached by combustion of a 
given quantity of fuel depend ? 

22. Mention five oxids occurring abundantly in nature. 

23. Mention several substances which are acted upon by oxygen at 
ordinary temperatures. 

24. Explain the effect of fine wire gauze when lowered over the 
flame of a lamp. Mention an important practical application of the 
principle involved. 

25. Compare the kindling temperature of hydrogen with that of 
carbon. What bearing has their relative kindling temperature on the 
production of light by illuminating gas? 

26. Explain the phenomenon of spontaneous combustion. 

27. What would occur if the temperature developed by the com- 
bustion of nitrogen were higher than its kindling temperature t 



CHAPTER VI 
NITROGEN 

Symbol N. — Atomic Weight 14 

46. Occurrence. — Xitrogen forms 4 of the bulk of the 
air. It is found in combination in a large number of sub- 
stances, e.g. in saltpetre or potassium nitrate, KN0 3 , and 
Chili saltpetre, XaX0 3 . It also occurs abundantly in am- 
monia, nitric acid, flesh, and other animal substances. Its 
compounds give to burned hair and woollens their peculiar 
odor. Many vegetable substances contain nitrogen, as cab- 
bage, mushroom, horse-radish, and it is an essential con- 
stituent of quinine, morphine, prussic acid, and strychnin. 
It forms a part of nearly all explosives, as nitroglycerin, 
gunpowder, etc. 

47. Preparation. — Nitrogen may be prepared by removing 
the oxygen from the air. Any method which burns up the 
oxygen of the air and forms solid or liquid products, yields 
nitrogen which is reasonably pure. If any of the products 
are gaseous they will be mixed with the nitrogen, which 
will therefore be impure. 

First Method. — Introduce a jet of burning hydrogen into 
a bottle of air. After the flame is extinguished there will 
remain in the bottle, nitrogen and the product of the com- 
bustion of hydrogen — H 2 0. 

39 



40 CHEMISTRY 

Second Method. — Phosphorus burns in the air forming 
phosphorus pentoxid, P 2 5 , a flaky white substance which is 
soluble in water. 

Experiment XXXIV. (See Experiment 28.) —Support a piece of 
chalk over water in the water pan by means of a wire standard. 
Make a hollow in the chalk, place a piece of dry phosphorus about the 
size of a pea in it. Ignite the phosphorus, quickly cover it with the 
large bottle so that the mouth of the bottle is under water. What 
chemical change takes place ? Notice any change in the volume of 
the air. Explain. Does all the air support combustion ? Take the 
bottle from the water pan (do not allow the water to escape) and 
shake it. What is the result? Does the white cloud which at first 
filled the bottle remain ? Test the gas with a lighted taper. Is it 
combustible ? Is it poisonous ? State its physical properties. 

Third Method. — If air be passed through a tube contain- 
ing heated copper filings, the oxygen combines with the 
copper, forming copper oxid, and nitrogen may be col- 
lected. Nitrogen prepared from the air will contain the J 
impurities which exist in the air. Pure nitrogen may be 
prepared as follows : — 

Fomih Method. — Heat ammonium nitrite and collect 
evolved gas over water. 

XIT 4 X0 2 = 2H 2 + 2K 

On account of the unstable character of ammonium 
nitrite, it is difficult to keep a supply on hand ; in practioJ 
therefore, a mixture of ammonium chlorid and sodium 
nitrite is usually substituted for the ammonium nitrite. 
When this mixture is heatcil the reaction proceeds accord- 
ing to the following equation: — 

NH4CI + XaX<\, = Na< '1+2 H 2 + X,. 

This method supplies tin- puresl nitrogen. 



NITROGEN 41 

48. Physical Properties. — The last experiment taught us 
certain physical properties of nitrogen; mention them. 
The following additional physical properties not easily 
shown experimentally are worthy of consideration. It is 
sparingly soluble in water, only 1.6 % being dissolved at 
10° C. It may be liquefied at — 193° under pressure of one 
atmosphere. It is slightly lighter than air. 

49. Chemical Properties. — Nitrogen combines directly 
with very few elements, and combination with these ele- 
ments is effected with difficulty. By indirect methods it 
can be made to combine with hydrogen, and with hydrogen 
and oxygen. Its chemical affinities are exceedingly feeble, 
and the compounds which it forms are very unstable. 
Gunpowder, nitroglycerin, and many other explosives are 
nitrogen compounds, and owe their characteristic properties 
to the ease with which they are decomposed. The rapid 
decay of animal and vegetable substances which contain 
nitrogen is a further illustration of the unstable character 
of nitrogen compounds. 

REVIEW QUESTIONS 

1. State the physical properties of nitrogen. 

2. State its chemical properties, activity, combustibility, relation 
to explosives, relation to decay. Is it poisonous ? 

3. What proportion of the air is nitrogen ? How is this shown ? 

4. Describe an experiment for obtaining nitrogen by the use of 
phosphorus. Give the name and formula of the fumes formed, and 
account for their disappearance. 

5. Compare oxygen with nitrogen with respect to (a) chemical 
activity, (6) occurrence, (c) number of compounds, (c?) relation to 
combustion and life, and (e) physical properties. 

6. Why is nitrogen an important constituent of most explosives ? 

7. What are nitrogeneous foods ? 



CHAPTER VII 

HYDROGEN 

Symbol H. — Atomic Weight 1 

50. Occurrence. — Hydrogen is never found uncoinbined 
in nature ; its compounds, however, are widely distributed. 
It forms i of the weight of water, and occurs in all 
animal and vegetable matter. It is the only substance 
common to all acids. 

51. Preparation by the Action of an Acid on a Metal. 

Experiment XXXV. — 1. Put a few pieces of granulated zinc in 
the test bottle. Cover them with dilute hydrochloric acid. What 
occurs ? 

2. After a minute or two hold a lighted match over the bottle. 
What occurs ? 




3. Put a few pieces of zinc in your generating bottle. In one hole 
in the rubber stopper pul a straight glass tube long enough to reach to 
the bottom of the bottle ; in the other fit a bent tube with a delivery 
tube attached. Pour enough dilute sulfuric acid into the bottle to 
cover the zinc. Collect the gas over water. 
42 



HYDROGEN 43 

Caution. — The gas is explosive when mixed with air ; when pure, 
it burns quietly. To determine when all the air which filled the 
bottle at the beginning of the experiment is driven off, collect a small 
bottle of gas ; when full, raise it from the water, mouth .downward, 
and apply a match. If the first bottle of gas explodes, repeat until a 
bottle of gas is obtained which burns quietly. 

4. Collect three bottles of pure gas. 

5. Place the first bottle, mouth upward and uncovered, on the 
table. After a few minutes, test it, to see whether or not it contains 
hydrogen. Is hydrogen lighter or heavier than air ? 

6. Pour the hydrogen in the second bottle upward into an inverted 
bottle containing air. Test each bottle with a match. Is there any 
hydrogen in the inverted bottle ? In the other bottle ? 

7. Light a candle with a wire attached for a handle. Hold the 
third bottle mouth downward and thrust the lighted candle well into 
the bottle. What occurs ? What burns ? Does the candle burn ? 
Withdraw the candle slowly. Is it alight ? Why ? Put it back into 
the hydrogen. Does hydrogen support combustion ? Is the mouth 
of the bottle heated ? 

Experiment XXXVI. The Philosopher' 1 s Lamp. (Optional.) — 
Remove the delivery tube and substitute for it a tube drawn out to 
a fine point. If you are sure that the gas is pure, i.e. if you have not 
taken the stopper out of the generating bottle since testing the gas, 
light the gas at the end of the pointed tube. Hold a cold dry bottle 
over the flame. What do you see in the bottle ? Where did it come 
from ? (Chemical examination proves it to be pure water. ) What is 
the product of the combustion of hydrogen ? 

Hydrogen may be prepared by several other processes ; 
for example, by decomposing water by electricity (Experi- 
ment 40) ; by decomposing water by metals at ordinary tem- 
peratures (Experiment 42) ; by passing steam over heated 
metals (Art. 72, etc.). 

The following equations represent chemical changes in 
the preparation of hydrogen by the action of an acid on a 
metal : — 

Zn + 2 HC1 = ZnCl 3 + 2 H. 



44 CHEMISTRY 

This is the reaction when hydrochloric acid is used. If 

sulfuric acid is used, the following equation expresses the 

reaction : — 

Zn + H 2 S0 4 = ZnS0 4 + 2 H. 

52. Physical Properties. — Pure hydrogen is odorless, and 
is the lightest known substance ; one litre of it at ordinary 
pressure weighing .08950 gramme. It may be liquefied 
by extreme cold and pressure, but is more difficult to 
liquefy than any other gas. It diffuses more rapidly than 
any other gas. Water dissolves only 2% of hydrogen. 

53. Chemical Properties. — In its chemical affinities hydro- 
gen closely resembles a metal; it has a strong affinity for 
oxygen, chlorin, and a few other elements, and the com- 
pounds which it forms with carbon indirectly are very 
numerous ; it is, however, very difficult to get it to combine 
directly with carbon. 

54. Comparison of Physical and Chemical Properties of 
Hydrogen and Oxygen. — Hydrogen will burn ; oxygen sup- 
ports combustion. Hydrogen has affinity for few sub- 
stances ; oxygen for many. Hydrogen is the lightest known 
substance. Oxygen combines readily with carbon, sulfur, 
phosphorus, and iron. It is difficult to get any of these 
elements to combine with hydrogen. The two elements 
have opposite chemical properties; yet in their physical 
properties they resemble each other. 

55. Uses. — On account of its great affinity for oxygen, 
hydrogen is extensively used for the purpose of extracting 
oxygen from compounds containing it, i.e. as a reducing 
agent. 

56. Heat and Chemical Energy of the Combustion of Hydro- 
gen. — The chemical affinity of hydrogen for oxygen is 



HYDROGEN 45 

greater than that of any other known substance. The heat 
produced by the combustion of hydrogen is therefore greater 
than that of any other substance. One pound of hydrogen 
in burning gives off 34,400 heat units ; that is, it develops 
enough heat to raise 34,400 pounds of water from 0° C. 
to 1° C. 

The oxyhydrogen blowpipe consists of a tube H (Fig. 5), 
through which hydrogen flows, and at the end of which 
it is ignited. In the centre of this is a smaller tube 




through which a stream of oxygen is forced into the flame. 
The flame produced gives very little light, but its tem- 
perature is between 2000 and 2200° C. ; it is, therefore, used 
in working platinum and other metals fused with difficulty. 
A piece of lime held in the flame is heated to incandes- 
cence, and emits a bright light equivalent to about 120 
standard candles. This device is known as the calcium 
light. 

Experiment XXXVII. — Take notes on the effect of the oxy- 
hydrogen blowpipe flame upon bits of lead, zinc, copper, steel, iron, 
glass, and calcium oxid. 

57. Burning of Oxygen or Air in Hydrogen. — If a jet of 

oxygen or air be introduced into a vessel containing hydro- 
gen, the oxygen or air may be ignited and will burn as 
readily as hydrogen burns in oxygen or in air. 

If a stream of hydrogen be passed through the tube H 
(Fig. 6), and ignited at the bottom of the bottle, a jet of 



46 CHEMISTRY 

air introduced through the hydrogen flame will burn with 
a flame of the same character as that produced when 
hydrogen burns in air. 

58. Product of this Combustion. — The combustion of 
hydrogen must form an oxid of hydrogen. Water is an 
oxid of hydrogen, and analysis of the moisture condensed 
on any cold object held over the hydrogen flame, proves 
that water is the product. 



H 



AIR OR OXYGEN 



59. Formation of this Substance in Ordinary Combustion. — 

Nearly all fuels contain hydrogen, and therefore form more 
or less water when they burn ; this can be shown by hold- 
ing a cold object over the flame. Moisture can thus be 
condensed over burning oil, wood, coal, gas, etc. When 
oxygen combines with the waste products of the body 
in the lungs, the hydrogen of the products is turned into 
water; thus the well-known cloud formed by the breath 
in cold weather is this moisture rendered visible by con- 
densation. This may be easily shown by breathing upon 
any cold dry object. 

REVIEW QUESTIONS 

1. Explain the cause of the moisture which appears on a lamp 
chimney when the lamp is lighted. 

2. Why ilces this film disappear? 

3. If water is a product of combustion, why does it not extinguish 
the lire? 



HYDROGEN 47 

4. State the symbol, atomic weight, and occurrence of hydrogen. 

5. Describe the process of preparing hydrogen from zinc and 
hydrochloric acid. Write the reaction. 

6. Discuss the physical and chemical properties of hydrogen. 

7. Describe the oxyhydrogen blowpipe. For what is it used ? 

8. Show how a jet of air may be burned in hydrogen. 

9. What does the moisture which gathers on a cold object held 
over a lighted kerosene lamp indicate as to the composition of the 
kerosene oil ? 

10. Discuss the heat and chemical energy of the combustion of 
hydrogen. 

11. State the color and odor of the gas prepared in Experiment 35. 

12. Is hydrogen explosive ? Under what conditions ? 

13. Does hydrogen combine with oxygen at ordinary temperatures ? 
at high temperatures ? 

14. Describe the hydrogen flame as to («) color, (6) amount of 
heat, (c) amount of light. 



CHAPTER VIII 

CHEMISTRY OF WATER 
Formula H 2 0. — Molecular Weight 18 

60. Occurrence of Water in Nature. — Three-fourths of the 
earth's surface is covered with water. It exists in the 
atmosphere, in all vegetable and animal matter, in the soil, 
and even in the rocks. 

Experiment XXX VIII. — Heat a small piece of alum in a test tube. 
Note evidence that it contains water. Is the loss of water accompa- 
nied by a change in the crystal ? Explain. Kepeat the experiment, 
using' pieces of gypsum, meat, potato, etc. 

61. Properties of Water. — At ordinary temperatures pure 
water is a tasteless, odorless, transparent fluid, colorless in 
thin layers, but distinctly blue when viewed in large masses. 
At its greatest density water is 773 times heavier than air. 

Many of the properties of water are used as standards by 
means of which we may express the corresponding proper- 
ties of other substances. The specific gravity of all solids 
and liquids expresses the relation between the weight of the 
substances and the weight of a like volume of water. 

The specific heat of all substances is similarly based upon 
that of water. In the metric system the unit of weight is 
the weight of a cubic centimetre of water, and the melting 
and boiling points of water are the standard temperatures 
used in the manufacture of thermometers. 

62. Solution. — Water dissolves a greater number of solid, 
liquid, and aeriform substances than any other solvent. 

48 



CHEMISTRY OF WATER 49 

The adhesion between the molecules of the dissolved sub- 
stance and those of water overcomes the cohesion of the 
substance dissolved, and it diffuses through the mass of 
water, forming a transparent solution in which the dissolved 
substance is invisible. Strongly colored substances, how- 
ever, impart their characteristic color to the solution. There 
is a limit to the amount of a substance which a solvent can 
dissolve at a given temperature and pressure, and a solution 
which contains all of a substance which it can dissolve is 
said to be saturated. 

We can now understand why solution aids chemical 
action. The molecules are no longer held firmly together 
by cohesion; they are free to move, and are thus easily 
brought into the intimate contact necessary to chemical 
action by their chemical affinities. 

If sugar is dissolved in water the solution seems to be 
simply a mechanical mixture ; there is no evidence that a 
chemical change has taken place; and if the solution is 
evaporated the sugar is recovered unchanged. This, there- 
fore, is a physical solution. 

In Experiment 9, marble was dissolved in hydrochloric 
acid and a chemical change was proven. Such solutions 
are called chemical solutions. 

63. The Effect of Heat on the Solution of Solids and Gases. — 
Physics teaches us that whenever a solid changes to the 
liquid form a certain quantity of heat is rendered latent. 
Hot water can supply this heat more readily than cold, and 
therefore solids are more rapidly dissolved by hot than by 
cold water. Furthermore, a larger quantity of most solids 
is dissolved by hot water than by cold. At high tempera- 
tures the cohesion of the molecules of a solid is less than at 
low temperatures, therefore there is less force to overcome 



50 CHEMISTRY 

in dissolving it. As the Avater cools, latent heat is with- 
drawn from a certain quantity of the dissolved substance, 
causing it to assume a solid state. 

When a gas is dissolved in a liquid its latent heat must 
be absorbed, but a cold liquid can absorb heat more rapidly 
than a warm one, and therefore a gas is more rapidly dis- 
solved in a cold liquid than in a warm one. As the tem- 
perature of a solution of a gas is raised, a portion of the heat 
is used to change the state of the dissolved gas and a por- 
tion is liberated in gaseous forms. 

64. Water of Crystallization. — Experiment 38 taught us 
that crystalline alum contained water, and that the alum lost 
its geometrical form when the water was driven off. Many 
other crystals are like alum in this respect, and there is evi- 
dence that the water which they contain is held in feeble chem- 
ical combination. The water of crystallization does not make 
the substance moist, as it would if absorbed mechanically, 
and further, a given substance requires a definite amount 
of water for each molecule of the crystal. Certain substances 
form two or more kinds of crystal, requiring different quan- 
tities of water ; and in some crystals the color depends upon 
the amount of water of crystallization. Cobalt chlorid is 
often used as a sympathetic ink because of the change in 
color produced by expelling the water of crystallization. 

In some crystals the water is held so feebly that they lose 
either the whole or a portion of- their water of crystallization 
when exposed to the air, and in so doing lose their particular 
geometrical form. This process is known as efflorescence. 

Other crystals absorb water from the air and assume 
other geometrical forms, in some cases absorbing enough 
water to dissolve the crystal. Such crystals are said to be 
deliquescent. 



CHEMISTRY OF WATER 51 

Experiment XXXIX. — Put a crystal of ferrous sulfate and a 
small piece of calcium chlorid on separate pieces of paper and expose 
them to the air for several days. Which is efflorescent ? Which 
deliquescent ? 

65. Hydroxids. — Strictly speaking hydroxids are com- 
pounds formed by replacing one atom of hydrogen in the 
molecule of water with an atom of another element or with 
a group of elements. 

Na + H,0 = NaOH + H 
CaO + H 2 = Ca0 2 H 2 . 

According to this definition most acids are hydroxids but 
chemists rarely apply the term to them, whereas, all chem- 
ists agree in calling a compound formed by the union of a 
metal with hydrogen and oxygen an hydroxid. 

These compounds, which are very important and which are 
discussed more fully in Chapter XII., are sometimes called 
hydrates, but the term is rather objectionable because the 
termination ate is used to distinguish a class of compounds 
to which the hydroxids do not belong. 

66. Electrolysis of Water. 

Experiment XL. (Performed by the instructor. ) — Take notes upon 
this experiment, answering all the following questions and describing 
the apparatus used. An electric current is passed through acidulated 
water from one lead or platinum electrode to another. Gas is evolved 
which is collected in two tubes. Where is the gas liberated ? How 
does the volume over the positive electrode compare with that over 
the negative ? What gas is collected over the positive electrode ? 
How do you know? What gas is collected over the negative elec- 
trode ? Does this experiment prove that water is composed of two 
elements and no more ? Is the volume of the water decomposed equal 
to the volume of the gases formed ? How do you know ? 

67. Synthesis of Water. 

Experiment X*LI. (Performed by the instructor.) — Eudiometer tube 
— a "U" shaped tube of glass about 18 inches long closed at one end, 
having two platinum wires inserted at opposite sides near the closed 



52 CHEMISTRY 

end. Fill the eudiometer tube with mercury and invert in a mercury 
bath. Introduce a certain amount of oxygen, removing the tube and 
bringing the mercury to a level in both arms. Read the amount of 
oxygen in the tube, filling the arm with mercury again. Introduce 
about twice as much hydrogen in a similar manner, determining the 
exact volume, placing the thumb over the end of the tube that is open, 
and wrapping the tube in a towel, pass an electric shock through the 
wire. An explosion occurs, and water is formed. Some of the gas 
remains in the tube. Testing this residual gas to determine whether 
it is hydrogen or oxygen and subtracting its volume from the quantity 
used, we determine the volume of the two gases which combined. 
This experiment proves that there are only two elements in water. 

68. Formation of Water by passing Hydrogen over Heated 
Oxid. — When mercuric oxid is heated, oxygen is liberated. 
If a stream of hydrogen be passed over a heated oxid, 
the hydrogen and oxygen combine to form water. When 
copper oxid is used, the following reaction takes place : — 

CuO + 2H = Cu+H 2 0. 
In this experiment if the weight of water formed be de- 
termined and the tube containing copper oxid be weighed 
before and after the heating, it will be found that f of the 
weight of w r ater came from the copper oxid, thus proving 
that f of the weight of water is oxygen. 

69. Composition of Water by Weight and by Volume. — 
Preceding experiments have shown that water contains 
twice as much hydrogen as oxygen, volume alone consid- 
ered, and that it contains eight times as much oxygen as 
hydrogen, iveight alone being considered. These two seem- 
ingly contradictory facts being proven, it follows that the 
single volume of oxygen must be eight times as heavy as 
the two volumes of hydrogen, and that equal volumes being 
considered, the oxygen is sixteen times as, heavy as the 
hydrogen. In considering the composition of a compound, 
care must be taken to distinguish between these two 



CHEMISTRY OF WATER 53 

methods of stating the composition, and it must be remem- 
bered that the volumes used are, in all cases, the volume in 
an aeriform state, and not the solid or liquid state. One 
further fact should be stated here : when two volumes of 
hydrogen combine with one volume of oxygen to form 
water they do not form three volumes of steam ; their vol- 
umes is condensed one-third, so that — 

2 vols, of hydrogen + 1 vol. of oxygen form 2 vols, of steam, 
and this is the way in which the composition of a substance 
by volume should be stated. For further discussion of this 
topic see p. 118. 

The composition of a substance by weight is the same in 
the solid as it is in the liquid and aeriform state. That of 
water may be stated thus : — 

2 parts (by weight) of hydrogen -f- 16 parts of oxygen form 
18 parts of water. 

70. Decomposition of Water by Metals. 

Experiment XLII. — 1. Fill a medium sized bottle with water and 
invert it in the yellow dish, which should be about half full of water. 

2. Thoroughly dry a small piece of wire gauze in the gas flame, 
roll around a lead pencil, so that it forms a cylinder that is double 
walled in all parts. Fold one end of the cylinder over and pinch the 
bend with a pair of pliers. Drop a piece of sodium the size of a pea 
into it, using the pliers as before. 

3. Lift the bottle slightly, but not enough to allow the water to 
escape, and thrust the wire gauze beneath it. After all action has 
ceased slip a glass plate under the mouth of the bottle and remove the 
bottle from the water pan, placing it right side up on the table. 

4. Test the gas with a burning match. Do you recognize the gas? 
How? Where did it come from ? Drop a piece of pink litmus paper 
in the bottle. Does it change color ? Does water from the laboratory 
faucet produce a similar change ? What became of the sodium. 

Explain concisely all that has occurred. The reaction is as fol- 
lows : — 

Sodium + Water = Sodium Hydroxid + Hydrogen 

Na + H 2 = NaOH + H 



54 CHEMISTRY 

Note. — Litmus paper is prepared by dipping strips of paper into 
an infusion of litmus. It turns red, when treated with an acid, and 
blue, when treated with an alkali. 

71. Decomposition of Water by passing Steam over Heated 
Metals. — Certain other metals which decompose water 
slowly or not at all at ordinary temperatures, decompose it 
easily at high temperatures. If steam be passed through 
a tube containing bits of iron heated to redness, it will be 
decomposed and hydrogen may be collected over water. 

3 Fe + 4 H 2 = Fe 3 4 + 8 H. 

Query. — How may the weights of hydrogen and oxygen resulting 
from the decomposition be determined in this experiment ? 

72. Water Gas. — At high temperatures carbon also de- 
composes water, and this fact is the basis of the process of 
manufacturing water gas. Steam is passed over highly 
heated coal or coke (carbon), which combines with the oxy- 
gen of the water, forming carbon monoxid (CO). The re- 
action is as follows : — 

C + H 2 = CO + 2H. 

Both carbon monoxid and hydrogen are combustible gases, 
they are both odorless, and burn with feebly luminous flames. 
To overcome these objections it is customary to enrich water 
gas by adding certain gases, obtained by decomposing naph- 
tha, which give the gas a distinct odor, and which greatly 
increase the amount of light produced.- The illuminating 
gas used in many of our cities is prepared by this process, 
but the increased value of the ammonia and of the tar 
obtained as by-products in the process of manufacturing 
illuminating gas from bituminous coal has rendered the 
economy of water gas questionable. As water gas is more 
poisonous than ordinary illuminating gas, laws have been 
passed in certain states prohibiting its use. 



CHEMISTRY OF WATER 55 

73. Oxidation and Reduction. — The process of abstract- 
ing oxygen from a body is called reduction. In the manu- 
facture of water gas the hot carbon abstracts the oxygen 
from the water, illustrating its use as a reducing agent. 
Carbon is extensively used in the reduction of ores to a 
metallic state. The union of a substance with oxygen is 
called oxidation, and the reagent which causes the oxida- 
tion is called the oxidizing agent. Nitric acid and potassium 
chlorate are excellent oxidizing agents, as will be noticed 
in several subsequent experiments. In Experiment 42 the 
sodium was oxidized by the water, but water is not among 
the better oxidizing agents. 

74. Natural Waters. — Absolutely pure water is never 
found in nature. The impurities which it contains are of 
two classes : first, the inorganic, or those derived from the 
rocks; and second, the organic, or those derived from the 
decay of animal matter or vegetable substances. Some of 
the impurities are held in solution, while others are sus- 
pended and carried along by moving water. The purest 
water found in nature is rain water, particularly that" which 
falls in country districts after it has been raining some 
time. But even rain water contains impurities ; as it falls 
through the air it washes it, removing those suspended 
matters which are always present in it, and dissolving small 
quantities of the gases of the atmosphere. As soon as the 
rain reaches the earth, its great solvent power is exerted 
upon the mineral matter with which it comes in contact, 
and it becomes more impure. An impure water is not neces- 
sarily unfit for household purposes. See Article 78. 

75. Spring Water always contains dissolved mineral mat- 
ter as well as a considerable quantity of carbon dioxide de- 
rived from the decomposition of plants. Waters flowing 



5Q CHEMISTRY 

through different strata would naturally contain different 
amounts and different kinds of minerals, and we therefore 
have various kinds of spring waters. Sulfur springs usually 
issue from rocks containing a decomposing sulfid. A line 
of sulfur springs across western New York marks the out- 
crop of the Hamilton shale which, in certain layers, contains 
a great deal of iron sulfid. The chalybeate springs contain 
some compounds of iron in the same way, and the effervescent 
waters have some gas in solution. The famous springs at 
Saratoga, N. Y, belonging to this class, contain carbon dioxid. 

76. River water differs from spring water because a part 
of it, at least, has not been filtered through porous rock 
and thus relieved of suspended matter. It is consequently 
turbid, while spring water is usually clear and sparkling. 
Sea-water contains a large amount of mineral matter, the 
average quantity being about 3.5 % of its weight. 

77. Hard Water. — Certain salts which are frequently 
present in natural waters prevent the formation of a lather 
with soap in the ordinary process of washing, and give to 
waters containing them the property known as hardness. 
The chief substances which produce this effect are the com- 
pounds of calcium and magnesium. Soap is decomposed 
by such waters, forming an insoluble, curdy precipitate or 
scum which prevents the cleansing action of the soap until 
all of the hardening salts have been removed. Hardness 
due to the presence of carbonates may be removed by boil- 
ing the water, and is called temporary hardness. Waters 
having this kind of hardness are common in limestone 
regions. The limestone is an impure calcium carbonate 
(CaC0 3 ), and is not soluble in water, but water containing 
carbon dioxid converts the calcium carbonate into an acid 
carbonate (CaH 2 (C0 3 ) 2 ) which is soluble. Permanent hard- 



CHEMISTRY OF WATER 57 

ness, or that which remains after prolonged boiling, is 
usually due to the presence of sulfates. 

78. Potable Waters, — The inorganic impurities found in 
natural waters are very rarely injurious to health. The 
organic impurities, however, are usually accompanied by 
living germs, or bacilli, by means of which such diseases 
as cholera, typhoid fever, diphtheria, etc., are propagated. 
The principal source from which these dangerous organic 
impurities are derived is the drainage of houses and vil- 
lages; and though waters thus contaminated may become 
pure again through the action of the air and sunlight, it is 
not safe to rely upon this method of purification in the 
water which is to be used for drinking purposes. 

It is of the greatest importance that the water used for 
drinking purposes should be as pure as possible ; to this end 
it should be frequently tested, and if there is the slightest 
suspicion of contamination, it should be thoroughly boiled. 

In general it may be assumed that springs, deep wells, 
and mountain rivers and lakes, are safe sources of water 
supply; that stored rain water and surface water from 
cultivated land are unreliable ; and that shallow wells and 
rivers, to which sewage gains access, are dangerous sources. 

79. Distillation and other Methods of Purification. — The 
best method of purifying water is by distillation. This 
process removes both organic and inorganic impurities ; and, 
when properly conducted, supplies a perfectly pure water. 
On shipboard the salt water of the ocean is distilled. 

Experiment XLIIL — Using a flask, distil 30 or 60 cc. of water. 
Under "Physical Properties " note color, taste, odor. What action 
has it upon litmus paper ? Does it leave a residue upon evaporation ? 
Answer same questions concerning some natural water. 

Boiling. — Thoroughly boiling water, renders most of the 
organic impurities harmless. Disease germs are destroyed 



58 CHEMISTRY 

and albuminous matter coagulated so that it may be readily- 
removed by nitration. 

Filtration does not remove the dissolved inorganic im- 
purities, — these can be removed only by chemical processes 
(see next article) ; but when properly conducted it removes 
both organic and inorganic suspended matter, including 
disease germs. 

Small charcoal or sand filters are more apt to contaminate 
the water passing through them than to purify it ; for after 
a few days' use, the filter becomes so saturated with germs 
that the filtered water contains more of them than it did 
before it was filtered. Unless the filter is so constructed 
that the charcoal or sand may be removed and exposed to 
air and sunlight, it is unsafe to use it. The wire strainers, 
sometimes called filters and made to be attached to faucets, 
may remove some of the suspended matter, but they do not 
remove the germs. The Pasteur filter, in which the water 
passes through a natural stone, is the most efficient small 
filter; the stone must be removed and boiled, or exposed 
to the air for oxidation of the organic matter, occasionally, 
otherwise germs will pass through the filter after a time. 

Chemical Methods. — Attempts are rarely made to purify 
water on a large scale by chemical processes. But such 
processes have been employed for many years by frontiers- 
men and in regions where no drinkable water exists. 

If alum is gradually added to impure water containing 
calcium carbonate, calcium sulfate is formed, carbon dioxid 
is evolved, and aluminum hydroxid is precipitated. The 
aluminum hydroxid entangles the organic matter present 
and settles with it to the bottom, leaving the water clear and 
sparkling. If the water contains an insufficient amount of 
calcium carbonate, it will not be rendered perfectly clear, and 
the deficiency must be supplied by adding sodium carbonate. 



CHEMISTRY OF WATER 59 

Ferric chlorid, iron borings, and potassium permanganate 
have each been used successfully in chemical processes of 
purifying water. 

80. Softening. — (a) Temporary Hardness. 

Experiment XLIV. — 1. Dissolve 1 gramme of soap shavings in 
10 cc. of distilled water in a test tube. Draw out one end of a glass 
tube, about \ inch in diameter, to a point thus : — 



This is to be used as a dropping tube. 

2. Test 10 cc. of hard water, made by passing carbon dioxid 
through lime water until it is clear, in a test tube as follows : Using 
the dropping tube, add a single drop of the soap solution to the hard 
water, shake the tube, repeat the operation as often as may be neces- 
sary to determine the number of drops required to produce frothing. 

3. Test 10 cc. of distilled water in the same way. What do you 
conclude concerning the relative values of hard and pure water for 
washing purposes ? 

4. Boil some of the hard water and test 10 c.c as before. How 
does this compare in value with the unboiled sample ? 

Boiling decomposes the soluble carbonates, expelling 
carbon dioxid and precipitating the insoluble carbonate. 
The "fur" which forms on the bottom and sides of the 
tea-kettle and the scale which forms on the shell and tubes 
of a steam boiler are each due to the repeated removal of 
carbonates from water by boiling. 

Clark's process of removing temporary hardness is quite 
extensively used by water-works engineers. The hardness 
is estimated, and the quantity of " milk of lime " required 
to transform the amount of soluble carbonate present into 
insoluble carbonate is then added. The reaction is as 
follows : — 

CaH 2 (C0 3 ) 2 + CaO = H 2 + 2 CaC0 3 . 



60 CHEMISTRY 

(b) Permanent Hardness. 

Experiment XL V. — 1. Test 10 cc. of hard water, made by dissolv- 
ing calcium sulfate in distilled water and filtering, as in Experiment 
44. Note the number of drops of soap solution necessary to produce 
frothing. Boil some of the above-mentioned hard water, and test as 
before. What effect does boiling have on permanent hardness ? 

The sulfates and chlorids of lime and magnesium are 
decomposed by sodium carbonate (common washing soda) 
with the following reaction : — 

CaS0 4 + Na 2 C0 3 = CaC0 3 + Na 2 S0 4 . 
The sodium sulfate produced has no effect on the soap, but 
water containing it should not be used for drinking pur- 
poses. Hence the use of washing soda for softening water. 

81. Natural Methods of Purification, (a) Action of the 
Air. — Disease germs die when exposed to the sunlight, and 
organic impurities are oxidized when exposed to the air. 
Therefore, impure water running through shallow streams, or 
over precipices in a thin sheet, tends to become pure again. 

(b) Filtration through beds of sand or porous rock 
removes suspended matter. It is in this way that most 
spring waters are rendered clear and transparent ; it should 
be remarked, however, that clearness is not unfailing evi- 
dence that water is healthful. 

(c) Sedimentation. — In ponds and lakes water is often 
rendered clear, the suspended matter settling to the bottom 
under the influence of the force of gravity. 

(d) Natural Distillation. — This is the most important 
method of purifying the water in nature. The sun is the 
source of heat, and since evaporation takes place at a 
temperature far below the boiling point, it occurs every- 
where and at all times, even in winter, and the amount 
evaporated every hour is enormous. The vapor rises to 
the upper atmosphere, and encountering cold currents is 



CHEMISTRY OF WATER 61 

condensed in microscopic particles which float in the air. 
These increase in size as they move about, and finally fall 
as rain. The purest water found in nature is rain water, 
particularly after it has rained some time. 

Mountain streams which flow over rocky beds, notably 
those which flow over beds of sandstone, have exceptionally 
pure waters. Water which flows over limestone dissolves 
some of the stone and becomes hard. 

Note. — It is suggested that students take advantage of the oppor- 
tunity offered by Experiments 46-48 to examine the water which they 
habitually use for drinking purposes. 

82. Tests for Organic Impurities. 

Experiment XLVI. — Fill a tall glass jar with water to be tested. 
Add a few drops of sulfuric acid, then add a weak solution of potas- 
sium permanganate, drop by drop, until the water assumes a violet 
tint. If organic matter be present, the color gradually grows lighter. 
If the color remains unchanged for an hour, the water may be con- 
sidered safe for drinking purposes. 

Kesslefs Test. — Xessler's reagent is prepared by mixing potassium 
iodid and mercuric chlorid, and adding caustic soda. It furnishes 
a very delicate test for free ammonia, which is evidence of decom- 
posing organic matter. 

A drop or two of the reagent added to water containing ammonia 
gives it a brown color ; the greater the amount of ammonia, the darker 
the shade of brown. In practice it is customary to concentrate the 
ammonia in 500 cc. of the water to be tested by distilling it with a 
small quantity of sodium carbonate, and testing the first 50 cc. of the 
distillate with Xessler's reagent. 

Experiment XLVIL Test for Chlorids. 
. Note. — The members of the class should secure samples of drink- 
ing water from as many sources as possible, including water from a 
shallow well, a deep well, a pond, and a stream. Distilled water and 
a solution of common salt will be required ; these are for comparison 
only, as distilled water contains no chlorin, and salt water a great 
deal. (Common salt is composed of sodium and chlorin.) 

1. Add a few drops of nitric acid, free from chlorin, to 25 cc. of 
the distilled water, then add a few drops of silver nitrate solution. 

2. Treat 25 cc. of the salt water in the same way. Compare this 



62 CHEMISTRY 

with the distilled water. How can you distinguish water containing 
chlorin from pure water ? 

3. Concentrate 50 cc. of the drinking water to be tested to 25 cc. 
by boiling, and repeat the test. 

Does it contain chlorin ? Compare your result with that of other 
members of the class, and answer the following questions : — 

Does the water from the shallow well become milky ? Does that 
from the deep well ? Which samples contain chlorin ? 

Sewage always contains chlorids, and hence if a drinking 
water is found to contain a chlorid, it is to be suspected, 
and the chlorin must be proved to come from some other 
source, or the water should be avoided. If a well is sunk 
near the sea, or near a deposit of rock salt, its water may 
be perfectly wholesome although containing a relatively- 
large amount of chlorids. 

83. Tests for Inorganic Impurities. — The presence of 
inorganic impurities is usually made known without a chem- 
ical test; the presence of hydrogen sulfid is detected by 
the odor, free carbon dioxid by effervescence, iron by the 
taste, and dissolved salts by the action of soap. 

The presence of solids in solution may be determined by 
evaporating a few drops of the water to be tested on clean 
platinum foil. If solids be present, a residue will remain 
on the foil. 

The fact that one usually desires to know concerning the 
inorganic impurities of water supplied for household use 
is its degree of hardness. 

Experiment XL VIII. To determine the Degree of Hardness. — Pour 
70 cc. of the water under examination into a flask. Add 1 cc. of 
"Clark's soap solution,' 1 insert a stopper, and shake thoroughly. 
Set it aside for two or three minutes ; if a lather does not remain on 
the surface of the water at this time, add a second cubic centimetre 
of the soap solution. Repeat this process until a permanent lather is 
obtained. The number of cubic centimetres of soap solution used 
is equal to the number of degrees of hardness, and is one greater than 
the number of grains of calcium carbonate per imperial gallon. 



PROBLEMS 69 

22. A litre of water weighs 1000 grammes ; how many grammes of 
hydrogen does it contain ? how many grammes of oxygen ? how many 
litres of each ? 

23. How many litres of the element in the first column may be 
obtained from 10 grammes of the substance in the second column ? 

H H 3 S0 4 

O H 2 S0 4 

O HN0 3 

H HN0 3 

N HN0 3 

H HC1 

CI HC1 

24. How many grammes of the substance in the first column will 
be required to prepare 10 litres of the element in the second column ? 

H 2 S0 4 

KCIO3 CI 

KCIO3 O 

Zn H 

H 2 O 



CHAPTER X 

COMPOUNDS OF NITROGEN AND HYDROGEN 

Nitrogex combines with hydrogen to form three com- 
pounds ; namely : — 

Ammonia, NH 3 

Hydrazine, N 3 H 4 

Hydrazoic acid, N 3 H 

AMMONIA 
Formula NH 3 . — Molecular Weight 17 

90. Occurrence. — Ammonia occurs in small quantities 
in the air, being formed under certain conditions by the 
decay of animal and vegetable substances. 

The chief source of ammonia is the ammoniacal liquor 
of the gas works, which is the water through which the 
gas has been passed to remove the ammonia formed by 
the decomposition of the coal. 

91. Preparation of Ammonia, NH 3 . 
Experiment XLIX. (For two students.) 

Note. — Experiment 50 may be performed with this one if the 
students will arrange the three bottles with tubes required before 
beginning this experiment. 

1. Mix 4 grammes of ammonium chlorid and 8 grammes of calcium 
hydrate on a piece of glass, adding a few drops of water. Place the 
mixture in a flask with a suitable delivery tube, add sufficient water 
to cover the mass, and apply heat. 

2. Collect three bottles of the gas by upward displacement. Set 
them aside, mouth downward. 

70 



COMPOUNDS OF NITROGEN AND HYDROGEN 



71 



3. Hold the Bunsen burner flame in a stream of the gas. Can you 
ignite it ? Does the gas burn while the burner is held in the stream ? 
Is the gas combustible '? Can its flame be said to have a color ? 

4. Connect the flask to the series of bottles described in Experi- 
ment 50, and proceed with that experiment. 

5. When leisure permits, test the three bottles of the gas in such 
manner as to enable you to answer the following questions : — 

Is it a supporter of combustion ? Is it heavier or lighter than air ? 
Is it soluble in water ? Test with a piece of moist pink litmus paper. 
Note the odor. Caution. 

When ammonia is prepared as above, the action is as 
follows : — 

CaHA + 2 NH 2 C1 = 2 NH 3 + CaCl 2 + 2 H 2 0. 

Ammonia is also formed when nitrogenous organic matter 
is heated out of contact with the air, as in the process of 
making illuminating gas by heating coal, or in the process 
of making animal charcoal. 




fri fTi iv* 



Ammonia gas is often prepared by heating the stronger 
ammonia water of commerce in a flask and collecting the 
gas as in Experiment 49. 

Ammonia water was formerly called spirits of hartshorn, 
because it was prepared by distilling the horns of the 
hart. 



72 



CHEMISTRY 



92. Preparation of Ammonium Hydroxid, NH 4 OH (Ammonia 
Water). 

Experiment L. (For two students.) — 1. Connect a series of 
three medium sized bottles with the delivery tube of the flask used 
in Experiment 49 as shown in Fig. 8. Have 20 cc. of water in the 
first bottle, and about 50 cc. in each of the others. The first and 
second bottles are fitted with rubber stoppers. Neither tube of the 
first bottle should dip below the water. The tubes by which the gas 
enters the remaining bottles should dip beneath the water. The gas 
is sometimes dissolved faster than it is supplied in a given bottle, and a 
vacuum is formed, causing the water to run into it from the next bottle. 
Should this occur, raise the stopper of the bottle toward which the 
water flows. If three-holed stoppers are at hand, it is best to use 
them, and to insert safety tubes in the first and second bottles, thus 
preventing this action. 

2. Hold a glass rod moistened with hydrochloric acid over a bottle 
of ammonia water. What occurs ? This is the test for ammonia. 
Test the ammonia water with litmus paper. 

93. Manufacturing Processes. — In the arts, ammonia is 
prepared either by adding slaked lime to the ammoniaeal 
liquor of the gas works, or by boiling the liquor. In 




the latter process the vapor is often passed into sulfuric 
acid, forming crude ammonium sulfate, which is used as 
a fertilizer. 

At the Rochester Ammonia Works the liquor is forced 



COMPOUNDS OF NITROGEN AND HYDROGEN 73 

into the generator G, Fig. 9, by a steam siplion S, and 
slaked lime is introduced through the pipe L. The mix- 
ture is agitated and heated, and the gas escapes through 
the delivery pipe D to the iron tanks C, where it is dis- 
solved in water as in Experiment 50. Between G and 
C, the gas passes through several cylinders containing 
petroleum and various other solvents which absorb im- 
purities, but allow the ammonia to pass through them. In 
this Avay, the " stronger ammonia water " of the drug stores 
is made. 

94. Liquid Ammonia. — There is a large demand for 
anhydrous ammonia for use in ice machines. It is usually 
prepared as follows : Ammonia water is heated in an iron 
cylinder A, Fig. 10. The 
gas, NH 3 , is driven over 
into the condenser C. As 
it accumulates, the press- 
ure increases until it 
reaches 130 pounds per 
square inch, when the gas 
is liquefied. 

95. Physical Properties. — Ammonia gas can be easily con- 
densed to the liquid form by cold and pressure. When the 
pressure is removed it passes back to the form of gas and 
absorbs heat in so doing. 

One volume of water dissolves 600 volumes of ammonia 
gas at ordinary temperatures. It condenses at ordinary 
temperatures at 6.9 atmospheres; at ordinary pressures it 
boils at — 33.7° C. and solidifies at — 75°. 

96. Chemical Properties. — A jet of ammonia to which a 
flame is applied continues to burn in oxygen after the 
flame is withdrawn. In air, however, the heat of com- 



A 


Fig. 10. 


C 


m 







74 



CHEMISTRY 



bustion is not sufficient to raise adjoining particles to the 
kindling temperature. 

In gaseous form as well as in the solution ammonia turns 
red litmus paper blue and neutralizes acids just as the alka- 
lies, sodium, and potassium hydroxids do. 

Ammonia combines directly with acids and many other 
substances to form a series of compounds which resemble 
each other in general properties, and each of which contains 
the group of atoms NH 4 . In its chemical action, therefore, 
this group resembles a metallic element, and in order to dis- 
tinguish it from ammonia, NH 3 , the termination um, which 
is applied to nearly all metallic elements, is substituted for 
the final a of ammonia. The similarity in composition of 
some of the compounds of ammonium, zinc, and sodium is 
shown in the following table : — 





NH 4 


Zn 


Na 


NH4CI 

(NH 4 ) 2 S04 
NH4NO3 


ZnCl 2 
Z11SO4 
Zn(N0 3 ) 2 


NaCl 

Na 2 S0 4 
NaN0 3 





Compounds which play the part of an element are called 
radicals. 

There is more or less evidence that a definite chemical 
compound is formed when ammonia is dissolved in water 
and that its formula is NH 4 OH. This compound has never 
been isolated, however, and certain chemists doubt its exist- 
ence. The name ammonium hydroxid implies that the 
solution is chemical rather than physical. 



97. Uses. — Ammonia is extensively used in the manu- 
facture of artificial ice, aniline colors, indigo, washing soda, 



COMPOUNDS OF NITROGEN AND HYDROGEN 75 

etc. It is also used in the laboratory as a reagent and in 
the household as a detergent. 

The following device illustrates the manner in which 
liquid ammonia is employed in making artificial ice: — 

Anhydrous ammonia flows from the tank LA into the 
chamber which surrounds a vessel of water I; it evapo- 
rates rapidly, and so much heat is rendered latent that the 
water is frozen. The gas is pumped back into the tank 
and again liquefied by pressure, and the operation is re- 
peated. 

In the Carre Ice Machine, a pound of coal is consumed 
for each pound of ice made. 



f 



U.A 



~l_ 



REVIEW QUESTIONS 

1. Describe the preparation of the ammonia of commerce. 

2. Describe the preparation of ammonia in the laboratory. 

3. Discuss the combination of ammonia with water. 

4. Distinguish between ammonia and ammonium ; between liquid 
ammonia and ammonia water. 

5. In what respect does ammonium resemble a metal ? 

6. What is hartshorn ? 

7. State the color, odor, solubility, and weight of ammonia. 



CHAPTER XI 
NITRIC ACID 

Formula HNO3. — Molecular Weight 63 

98. Occurrence. — Nitric acid is formed in the air in 
small quantities during thunder storms, and is washed to 
the earth by rain, where it combines with elements found 
in the soil. 

The compounds of nitric acid and the metals potassium 
and sodium occur abundantly in certain localities, particu- 
larly in India, where the waste products of animal life 
found near the villages are rapidly oxidizing, forming 
potassium nitrate (saltpetre), and in a desert tract in Chili, 
where the oxidation forms sodium nitrate, or Chili salt- 
petre. It has been suggested that this tract was at one 
time covered by the sea, and that the nitric acid was 
formed from the oxidation of sea-weeds and animals. 

In the economy of nature no substance, however obnox- 
ious, is lost, and the formation of these nitrates illustrates 
one method by which the vast army of living organisms in 
the soil converts waste material into useful and wholesome 
forms. 

99. Preparation. — Nitric acid is prepared by distilling 
either potassium or sodium nitrate with sulfuric acid. 

Experiment LI. — Place 15 grammes powdered potassium nitrate in 

a flask. Add 10 cc. strong sulfuric acid. Heat the flask on a sand 

bath, and condense the vapor in a test tube placed in a bottle of cold 

water. As the mixture begins to boil, drops of liquid will form on the 

76 



XITRIC ACID 77 

sides of the flask and run down into the mixture. After a short time 
the lower part of the flask appears dry, and the drops of liquid are 
observed on the neck of the flask. As the action progresses, more and 
more of the flask appears to he dry. Explain this action. Describe 
the acid obtained as to state, color, odor, action on litmus. Describe 
the substance which remains in the flask. 

100. Reaction. — At high temperatures the following 
reaction occurs : — 

2 KX0 3 + H,S0 4 = 2 HX0 8 + K 2 S0 4 . 

If the temperature be lower, the reaction becomes : — 
KX0 3 + H 2 S0 4 = HXO3 + HKS0 4 . 

101. Physical Properties. — Pure nitric acid is a colorless 
liquid about 1^ times as heavy as water. The nitric acid of 
commerce usually contains 40 to 60 % of water and a small 
amount of nitrogen peroxid, which gives to it its color. 

102. Chemical Properties. — Xitric acid is the most un- 
stable of the common acids j 76 % of its weight is oxygen, 
and the ease with which it is decomposed leads to its exten- 
sive use as an oxidizing agent. The first steps of the 
process of making sulfuric acid illustrate this action. 

As was shown in Experiment 35, when a metal is dis- 
solved in hydrochloric acid, hydrogen is evolved. When a 
metal is dissolved in nitric acid, however, no hydrogen is 
given off, but the result is the same as though hydrogen 
was first set free and afterward took oxygen from some of 
the remaining nitric acid, forming water and reducing the 
acid to one or more of the oxids of nitrogen represented by 
the following formulae, K 2 0, jSTO, jST0 2 , or even to ammonia 
or nitrogen. The interesting point here is the fact that 
when hydrogen gas is passed through nitric acid it does not 
decompose the nitric acid molecule, while in the case under 



78 CHEMISTRY 

consideration the hydrogen from the nitric acid molecule 
does decompose it. Instances of the increased chemical 
activity of elements which are taking part in certain 
chemical changes are quite numerous, and the cause of the 
increased activity is fully discussed in § 179 on the nascent 
state. 

Further chemical properties are illustrated in the follow- 
ing experiments : — 

Experiment LII. Nitric Acid as an Oxidising Agent. — Place a 
cubic centimetre of powdered charcoal on a piece of sheet iron, apply 
heat until the charcoal begins to glow. Using a clean glass tube, drop 
a few drops of concentrated nitric acid on the red hot charcoal. 
What occurs ? Account for the explosion. 

Alternate. — Pour a few cubic centimetres of concentrated nitric 
acid into a test tube. Partly close the open end of the test tube with 
absorbent cotton, holding the tube with the test-tube holder and over 
the yellow dish so as to catch the acid in case the tube breaks. Boil 
the acid. 

Describe, and account for the action observed. 

Experiment LIII. Nitric Acid as a Solvent. — Test the solubility 
of the following metals : tin, lead, zinc, copper, iron, gold, and silver 
in dilute nitric acid. If any of the metals fail to dissolve, apply heat. 
Determine whether hot concentrated nitric acid will dissolve any of 
the metals not acted upon by the hot dilute acid. 

Write the reactions. 

Note. — The symbol of copper nitrate is Cu(N03)2, and those of 
other nitrates are similar to it. 

Experiment LIV. Action of Nitric Acid on Various Substances. — 
In a medium sized bottle containing dilute nitric acid place a small 
piece of each on the following substances: white kid, white flannel, 
white silk, cotton, linen, asbestos, and bleached hemp ; stir them occa- 
sionally with a glass rod. Describe any change of color observed. 
Determine whether the color is permanent by endeavoring to wash it 
out. Which of the substances are dyed ? Which are mineral sub- 
stances ? which vegetable ? which animal '? Inference ? 

Experiment LV. Etching. — Cover the metal to be etched with 
melted paraffin ; after the wax has cooled sketch the design with a 



NITRIC ACID 79 

sharp instrument, taking care to cut through the paraffin. Cover the 
design with nitric acid, which dissolves the metal where the paraffin 
has been removed, and thus etches the design on the plate. After a 
few minutes wash off the acid and remove the paraffin. 

103. Uses of Nitric Acid. — Nitric acid is used in etch- 
ing, dyeing, oxidizing silver, and in the arts; for example, 
in the manufacture of nitroglycerin, guncotton, sulfuric 
acid, and as a solvent for silver in the processes of pho- 
tography. 

REVIEW QUESTIONS 

1. How are the plates used in printing " etchings" prepared ? 

2. State the occurrence of nitric acid in nature. Is it ever found 
uncombined ? 

3. How does the nitric acid of commerce differ from the chemi- 
cally pure article ? 

4. State the properties and uses of nitric acid, and describe its 
preparation. 

5. For what purpose is sulfuric acid used in the manufacture of 
nitric acid ? 

6. Account for the unstable character of nitric acid. 

7. Why is nitrogen an important constituent of most explosives ? 



CHAPTER XII 
ACIDS 

BASES AND SALTS 

104. Metallic and Non-metallic Oxids. — It will be remem- 
bered that oxygen combines with every element except 
fluorin, forming oxids. Most of these oxids combine with 
water to form hydroxids which belong to one of two classes 
possessing opposite chemical properties, for example, the 
following oxids form acids when treated with water 

Non-metallic Oxids. 

Sulfur dioxid, S0 2 +H 2 = H 2 S0 3 , sulfurous acid. 

Sulfur trioxid, S0 3 -f H 2 = H 2 S0 4 , sulfuric acid. 

Carbon dioxid, C0 2 +H 2 = H 2 C0 3 , carbonic acid. 
Nitrogen trioxid, N 2 3 + H 2 = 2HN0 2 , nitrous acid. 
Nitrogen pentoxid, N 2 5 -|-H 2 = 2 HN0 3 , nitric acid. 

Those included in the following list are called bases. 

Metallic Oxids. 

Sodium oxid, Na 2 0+H 2 = 2 Nail 0, caustic soda. 
Potassium oxid, TL,0 +H 2 = 2KH0, caustic potash. 
Calcium oxid, CaO +H 2 = CaH 2 2 , slaked lime. 
Ferric oxid, Fe,0 3 +3 H 2 = Fe 2 H G 0,5, ferric hydroxid. 

The oxids which form these compounds are distinguished 
as acid-forming oxids and basic oxids. This classification 
is not complete, as some oxids have neither acid nor basic 
properties, e.g. water, HX), nitrous oxid, N 2 0, etc. ; and 



BASES AND SALTS 81 

certain oxids act either as acid-forming or basic oxids, 
depending upon the element with which they combine ; but 
the importance of the two classes, and of the compounds 
formed when they unite, makes a somewhat extended study 
of their properties desirable. The metallic elements, or 
those which form basic oxids, are much more numerous 
than the non-metallic, or those which form acids, there 
being only fifteen of the latter. 

105. Definitions. 

Acid. — A compound containing one or more atoms of 
hydrogen which may be displaced by a meted. 

Base. — A compound containing hydrogen, oxygen, and a 
metal which may be displaced by the hydrogen of an acid. 

Salt. — A compound formed ichen a meted replaces one or 
more atoms of hydrogen in an acid. 

Salts are sometimes formed by direct union of an acid- 
forming oxid and a basic oxid, in which case the salt is the 
only product of the action ; when an acid combines with a 
base, however, the acid liberates hydrogen, taking the metal 
of the base and forming a salt ; and the liberated hydrogen 
of the acid with the hydrogen and oxygen of the base form 
water. 

106. Characteristics of the Stronger Acids. 
Acids have a strong affinity for all bases. 
They are all soluble in water. 

They have a sour taste. 

They turn vegetable blues red. 

They decompose carbonates. 

They combine with alkalies, losing their own properties 
and destroying those of alkalies. 

The only element common to all acids is hydrogen. 
^Nearly all acids contain both hydrogen and oxygen, but a 



82 CHEMISTRY 

few are binary. The most notable of these are formed by 
the union of hydrogen with some member of the chlorin 
family, but there are some others, such as the compound of 
hydrogen and sulfur, sometimes called hydrosulfuric acid, 
and the compound of hydrogen and nitrogen known as 
hydrazoic acid. 

107. Rules for Naming Acids. — The terminations "ous" 
and " ic " are applied to acids, and indicate the amount of 
oxygen in the compound, just as they do when applied to 
oxids : thus HN0 3 is nitric acid, and HN0 2 is nitrous acid. 

All the binary acids end in "ic," and have the prefix 
"hydro." The prefix "per" indicates more oxygen than 
the " ic " acid, and the prefix " hypo " less oxygen than the 
" ous " acid, e.g. : — 

HC1, Hydrochloric acid 
HC10, Hypochlorous acid 
HC10 2 , Chlorous acid 
HCIO3, Chloric acid 
HCIO4, Perchloric acid 

108. Characteristics of the Bases. — The properties of the 
bases are in a general way opposite to those of acids. They 
restore colors reddened by acids, and turn vegetable colors 
blue. 

109. Rules for Naming Salts. — The name of the salt 
formed when a given acid combines with a base, consists of 
two parts. 

First Part. — The name of the metal replacing the hydro- 
gen of the acid. 

Second Part. — The name of the acid modified in accord- 
ance with the following rules : — 



BASES AND SALTS 83 

Rule I. — Names of acids containing oxygen, ending in 
" ic," have the termination changed to "ate," e.g.: — 

Nitric acid forms nitrates. 
Acetic acid forms acetates. 
Sulfuric acid forms sulfates. 

Rule II. — Names of acids containing oxygen, ending in 
" ous," have their termination changed to " ite," e.g. : — 

Nitrous acid forms nitrites. 
Chlorous acid forms chlorites. 
Sulfurous acid forms sulfites. 

Rule III. — TJie prefix " hydro " is dropped from the 
name of the binary acids, and the termination "ic" is changed 
to u id," e.g. : — 

Hydrochloric acid forms chlorids. 
Hydrocyanic acid forms cyanids. 
Hydrofluoric acid forms fluorids. 

REVIEW QUESTIONS 

1. "Write the names of the salts formed by the union of the follow- 
ing bases with hydrochloric, nitric, sulfuric, chlorous, nitrous, hydro- 
cyanic, sulfurous, and chloric acids : — 

Sodium hydroxid, NaHO 
Potassium hydroxid, KHO 
Calcium hydroxid, CaHO 

2. Write the names of the salts formed by the action of each of the 
above acids on the following basic oxids : — 

Lead oxid, PbO 
Copper oxid, CuO 
Silver oxid, AgO 

3. Define and illustrate acid, salt, base. 

4. State how a binary compound is named. Illustrate. 

5. State and illustrate the meaning of hypo, per, id (ide), ate, ous. 

6. State and illustrate five principles of chemical nomenclature. 

7. State the characteristics of the stronger acids. 



CHAPTER XIII 
COMPOUNDS OF NITROGEN AND OXYGEN 

110. Nitrogen combines with oxygen to form five distinct 
compounds having the following compositions : — 

Nitrogen monoxid, N 2 

Nitrogen dioxid, N 2 2 or NO 

Nitrogen trioxid, N 2 3 

Nitrogen tetroxid, N 2 4 or N0 2 

Nitrogen pentoxid, N 2 5 

111. Nitrogen Monoxid was formerly called nitrous oxid. 
It is also known as laughing gas. It does not occur in 
nature. 




(a) Preparation. 

Experiment LVI. (Two students work together.) — 1. Place 15 
grammes ammonium nitrate (NH 4 N0 3 ) in a flask. Connect this with 
a dry bottle placed in a dish of water ; from this bottle lead the gas to 
the water pan, as shown in the sketch. Heat the flask very gradually ; 
if too high a temperature is reached, nitric oxid may be formed and 
an explosion may occur. 

84 



COMPOUNDS OF NITROGEN AND OXYGEN 85 

2. Collect five bottles of the gas. The first bottle will be mixed 
with air ; throw it away. Do not allow all of the ammonium nitrate 
to boil away. 

3. Test the second bottle with a glowing splinter. Does the gas 
support combustion ? 

4. Remembering that combustion is a union with oxygen, answer 
the following questions : — 

Is the nitrous oxid decomposed ? Does nitrous oxid cause a glowing 
splinter to burst into flames ? Note the color, odor, taste of the gas. 

5. Remove the third bottle from the pan when about \ full of gas. 
Cover the mouth of the bottle with the hand and shake vigorously. 
Is a vacuum formed ? Is the gas soluble ? 

6. Lower a small piece of burning phosphorus into the fourth 
bottle. What occurs ? Ignite a small amount of sulfur with a 
match and lower it into the fifth bottle. Does it burn ? If not, 
use a Bunsen burner to ignite the sulfur, and see that it is burning 
vigorously before you test the gas. Explain the action. 

7. Examine the condensing bottle, and so state the source of the 
liquid it contains. Has it an odor or a taste ? Compare the taste 
with that of ammonium nitrate. Has any of the ammonium nitrate 
been carried over into the condensing bottle without chemical change ? 

Reaction : NH 4 N0 3 = N 2 + 2 H 2 0. 

(b) Properties. 

In addition to the properties already shown nitrogen 
nionoxid possesses the following characteristic properties : — 

When inhaled it produces a kind of intoxication usually 
manifested by hysterical laughing; hence its name. If 
more of the gas is inhaled, this is followed by unconscious- 
ness, lasting a few minutes. It is well adapted to use as 
an anaesthetic in minor surgical operations, but special care 
must be taken that the gas used for this purpose be pure ; 
if made from ammonium nitrate, containing ammonium 
chlorid, the gas always contains chlorin; if heated too 
strongly, ammonium nitrate yields nitric oxid and possibly 
hyponitrous acid. If either of these is present, the gas is 
unfit to breathe. It may be freed from these substances, 
however, by agitation with ferrous sulfate solution. 



gg CHEMISTRY 

When liquid nitrogen monoxid is evaporated in a vac- 
uum with carbon disulfid, it produces the remarkably low 
temperature — 140° C. 

AVater at 0° C. dissolves a little more than one volume of 
the gas. 

When slightly heated in an atmosphere of this gas 
metallic potassium and sodium burn brightly, forming 
oxids ; if strongly heated, nitrates are formed. 

112. Unstable Characteristics of Nitrogen Monoxid and 
Ammonium Nitrate. — In Experiment 56 the feeble affinity 
which binds the elements of ammonium nitrate together 
was illustrated. At ordinary temperatures it is a stable 
compound, but at a temperature somewhat above its melting 
point the compound is decomposed, forming nitrous oxid 
and water as indicated in the equation on page 85. If 
the temperature is too high, nitric oxid and water are 
formed, leaving one-half of the nitrogen in the free state. 

NH 4 N0 3 = 2 H 2 + NO + N* 
The so-called ability of nitrous oxid to support combus- 
tion is due to and is an illustration of its unstable character. 
In all cases it is the oxygen of the nitrous oxid which 
supports combustion, and the phenomenon is preceded by 
the decomposition of the gas. 

113. Nitrogen Dioxid was formerly called nitric oxid. 
Its molecular formula is believed to be NO instead of N^OJ 
because its density is 15, and if the latter formula was 
chosen it would be an exception to the rule that the density 
of any compound gas is half its molecular weight. It does 
not occur in nature. 

(a) Preparation. 

Experiment LVII. (Performed only under hood.) — Place a small 
handful of copper clippings in a generating bottle, and arrange appa- 



COMPOUNDS OF NITROGEN AND OXYGEN 87 

ratus as for the preparation of hydrogen, Experiment 35. Pour about 
50 cc. of water into the generating bottle, and add an equal quantity of 
nitric acid. 

Look for evidence of the formation of a colored gas, a colorless 
gas. a soluble gas. 

Collect six bottles of the gas, pour the liquid of the generating 
bottle into the copper nitrate bottle, rinse the copper which remains 
in the bottle with plenty of water, and put it away to be used again. 
Note the color of the gas collected, the color of the liquid in the 
generating bottle. 

1. Remove the cover of the first bottle. Do you note any change 
in color ? Is it possible that this bottle contains air only ? 

2. Allow the gas in the second bottle to escape into the air. What 
change of color occurs ? Which of the elements in the air is most 
active, and therefore most likely to be the cause of the change ? Does 
the colored gas formed resemble that formed in the generating bottle 
at first ? How do you account for this ? Does the colored gas seem 
heavier, or lighter than air ? If the colored gas is formed by oxidation 
of the colorless gas, how should their densities compare ? 

3. Hold the third bottle in a horizontal position, and while in this 
position remove the glass plate which covers it. Notice whether air 
diffuses into the upper or the lower part of the bottle. What does 
this show as to the relative weight of air and nitric acid ? 

4. Lower a lighted candle into the fourth bottle. Result ? Ignite 
some sulfur in an ignition spoon, and when it is burning vigorously 
lower it into the same bottle. Result ? Remove all traces of sulfur 
from the ignition spoon, cool it with water, dry it, and place a small 
piece of dry phosphorus in it. Ignite the phosphorus by touching it 
with a hot wire, and quickly lower it into the fourth bottle. Result ? 

5. Ignite a piece of phosphorus, and when it is burning actively 
lower it into the fifth bottle. Result ? Nitric oxid contains a larger 
percentage of oxygen than nitrous oxid. In the light of this fact how 
can you explain the difference in the behavior of the two gases ? 

6. Pour a few drops of carbon disulfid into the sixth bottle ; after 
a few minutes apply a lighted match. Describe the result. What is 
deposited on the sides of the bottle ? 

Reaction. — The reaction may be considered as taking 
place in two stages. First, 

Cu + 2 HX0 3 = Cu(N0 3 ) 2 + 2 H. 
The hydrogen, however, does not appear as a gas, but passes 



88 CHEMISTRY 

directly from the nitric acid molecule, from which it has been 
displaced, into combination with the hydrogen and oxygen 
of other molecules of nitric acid, as shown by the equation, 
6 H + 2 HN0 3 = 4 H 2 + 2 1S T 0. 
Complete the following reaction, which expresses both 
of the above changes : — ^ 



-THoO. 



3 Cu + 8 HN0 3 = 3 Cu(N0 3 ) 2 + ?NO • 
The hydrogen is said to be in the nascent state ; see § 179. 

(5) Properties. 

When strongly heated, metallic potassium decomposes 
nitric oxid and burns brightly, but metallic sodium remains 
unchanged. It is not easily coudensed to a liquid, requir- 
ing a pressure of more than a hundred atmospheres at a 
temperature of 11° C. Its most important chemical prop- 
erty was illustrated by its behavior in air. 

114. Nitrogen Tetroxid or Nitrogen Peroxid, N0 2 . — The red- 
dish brown gas noticed in Experiment 57 is nitrogen per- 
oxid. It has a disagreeable odor and is poisonous. It is 
heavier than air (it is warm when first formed and rises) 
and is very soluble in water. At 9° C. it solidifies to color- 
less crystals. The bonds which hold the oxygen to the nit- 
rogen in this compound are not nearly so strong as in nitric 
oxid, and upon this fact depends its value as an oxidizing 
agent, as illustrated in the process of manufacturing sulfuric 
acid. Metallic potassium bursts into flame in this gas. 

115. Nitric Oxid and Nitrogen Peroxid as Reducing and 
Oxidizing Agents. — In nitric oxid the oxygen is held rather 
firmly by the nitrogen, and there seems to be a demand for 
more oxygen. The action of this substance as a reducing 
agent depends upon its ability to take oxygen from other 
substances (a limited number) as illustrated by the forma- 
tion of nitrogen peroxid in Experiment 57. 



COMPOUNDS OF NITROGEN AND OXYGEN 89 

When the additional atom is obtained, the compound is 
held together by a very feeble affinity, and nitrogen peroxid 
is an excellent oxidizing agent; it gives up its oxygen 
to substances having but little affinity for it. 

REVIEW QUESTIONS 

1. State the physical properties of nitric oxid : («) color, 
(b) weight, (c) odor, (d) solubility, (e) liquefaction. 

2. Compare the chemical properties of nitrogen monoxid "with 
those of the dioxid. 

3. Is there any evidence that the oxygen is held with stronger 
bonds in nitrogen dioxid than in the monoxid ? 

4. Arrange phosphorus, sulfur, and nitrogen in the order of their 
affinity for oxygen as shown in Experiment 58. 

5. What chemical property enables us to distinguish oxygen from 
nitrogen monoxid ? 

6. What physical property enables us to distinguish oxygen from 
nitrogen monoxid ? 

7. Discuss the physical properties of nitrous oxid as follows : — 
(a) taste, (&) odor, (c) color, (cZ) weight, (e) solubility. 

8. Distinguish between oxygen and nitrous oxid with respect to 
(a) taste, (6) solubility, (c) chemical energy, (cZ) affinity for sulfur. 
What chemical properties has nitrous oxid ? 

9. State the chemical and physical properties of nitrogen tetroxid. 

10. Describe an experiment illustrating the unstable character of 
nitrogen compounds. 

11. Describe an experiment illustrating the unstable character of 
ammonium nitrate. 

12. Describe the ordinary preparation of nitrous oxid and name the 
property of nitrogen which makes this preparation easy. 

13. Describe an experiment to show the unstable character of 
nitrogen monoxid. 

14. Name five binary compounds of nitrogen and oxygen, and after 
each name write its formula. What law is illustrated by these com- 
pounds ? 

15. Define oxidizing agent ; reducing agent. What compound of 
nitrogen is used in oxidation ? reduction ? Why ? 

16. Explain the difference in the behavior of potassium when 
slowly heated in atmospheres of nitrous oxid, nitric oxid, and nitrogen 
peroxid. 



CHAPTER XIV 
THE CHLORIN FAMILY 

116. The elements fluorin, chlorin, bromin, and iodin 
resemble each other in chemical affinities and other proper- 
ties, and are, therefore, treated as members of the same 
family. They are sometimes called the halogens. 

SECTION I.— CHLORIN 
Symbol Cl. — Atomic Weight 35.5 

117. Occurrence. — Chlorin does not occur free in nature, 
but its compounds are widely distributed and very abun- 
dant. Common salt, which is present in large quantities in 
sea-water, is sodium chlorid, NaCl ; sea-water also contains 
chlorids of magnesium and potassium. Horn silver, one of 
the most important ores, is silver chlorid, AgCl ; and all 
plants contain the chlorids of potassium and sodium. 

118. Preparation. — (a) First Method. From Bleaching 
Powder. (Chlorid of Lime.) (To be performed only under 
the hood.) 

Experiment LVIII.—Tl&ce 15 grammes of bleaching powder in a 
flask, and pour through a funnel tube about 30 cc. of dilute sulfuric 
acid. Collect the gas by displacement of air. 

In the arts this process is extensively used. Paper rags 
are boiled in alkali to remove the grease, then placed in 
a large vat with bleaching powder and sulfuric acid ; when 
90 



THE CHLORIN FAMILY 



91 



they come out they are a pure white. Cotton cloth is 
bleached by passing it through alternate vats of sulfuric 
acid and chlorid of lime. 



(b) Second Method 



Experiment LVIX. (Performed 
12 grammes manganese dioxid, 
Mn0 2 , and enough hydrochloric 
acid, HC1, to cover it, in a 
flask, and gradually apply heat. 
Collect three bottles of gas by 
downward displacement of air, 
as shown in sketch. Now sub- 
stitute for the dry bottle a bottle 
nearly full of water, and allow 
the gas to bubble through it for 
a time. Note the color, odor, 
solubility, and weight of the gas. 



From Hydrochloric Acid. 

by the instructor.) — Mix 



w) 



f 



iQ 



7\ 



Fig. 13. 



Reaction : 



MN0 2 + 4 HC1 = 2 H 2 + 2 CI + MnCl 2 . 



Experiment LX. Affinity of Chlorin for Metals. — Throw a small 
amount of powdered antimony into a jar of chlorin. What occurs ? 
Is this combustion ? 



Experiment LXI. Affinity of Chlorin for Hydrogen. — 1. Prepare 
hydrogen as directed in Experiment 35. When the gas is pure, fit the 

generating bottle with a jet, as 

shown in this figure ; light the 

hydrogen, and introduce the jet 

into the second jar of chlorin. 

Does the hydrogen burn ? Is 

there any change in the color 

of the flame ? in the color of 

the contents of the jar ? Hold 

a piece of moist blue litmus 

Fig. 14. paper in the jar. What new 

substance is present ? 

2. Introduce a burning candle into the third bottle of chlorin, and 

note what takes place. State any explanation of the difference in the 




92 CHEMISTRY 

results obtained in this experiment and in the preceding one that 
occurs to you. 

3. Moisten a bit of tissue paper with warm turpentine and drop it 
into the fourth bottle of the chlorin. What occurs ? 

Turpentine is composed of carbon and hydrogen. In the 
above experiment the hydrogen is taken by the chlorin, and 
the carbon is liberated as " smoke." 

If chlorin water is exposed to sunlight long enough (say 
several days), it is found that oxygen is set free, the chlorin 
having taken the hydrogen from the water, leaving the 
oxygen. If any substance that has an affinity for oxygen 
is present in the water, the chlorin acts more rapidly. 

Experiment LXII. Affinity for Hydrogen. Bleaching. — 1. In 
the fifth bottle of chlorin place a moistened rose. What occurs ? 

2. In another bottle drop a piece of moist, colored calico. 

3. Write your name in ink, and pour some of the chlorin water 
made in Experiment 60 over it. 

4. Try the effect of chlorin water on printers' ink. All except one 
of the coloring matters tested are attacked by oxygen in the nascent 
state. Which one was not ? 

In bleaching, the chlorin may sometimes act directly on 
the coloring matter, but very frequently its action is due 
to its tendency to take hydrogen from water, thus making 
it easier for other substances to obtain oxygen. Chlorin 
is, therefore, often called an oxidizing agent. Its action 
as a disinfectant is somewhat similar to its action as a 
bleaching agent. 

119. Physical Properties. — Chlorin is 2\ times heavier 
than the air. One litre weighs 3.167 grammes. One volume 
of water will dissolve two volumes of chlorin. The name 
chlorin is derived from the Greek word meaning green. 

At ordinary pressures chlorin may be liquefied at — 34° C. ; 
a pressure of six atmospheres is required at 0° C. 



THE CHLORIN FAMILY 93 

120. Chemical Properties. — Clilorin combines with most 
substances at ordinary temperatures, and is remarkably 
active. It lias a marked affinity for hydrogen and for 
metals, as is shown by the large number of chlorids known. 
If inhaled in concentrated form, death will result. It com- 
bines With hydrogen with explosive violence when the 
mixture is heated, or even exposed to the sunlight. 

121. Uses. Bleaching. — Chlorin is extensively used in 
the arts as a bleaching agent. It destroys the molecules of 
vegetable coloring matter by replacing its hydrogen, or by 
adding oxygen. Moist articles bleach very rapidly because 
the water is decomposed by the chlorin, and nascent oxygen 
assists in the destruction of the coloring matter. 

Disinfection. — Chlorin is one of the best disinfectants we 
have. It is this substance that our health officers depend 
upon to keep cholera out of the country. Liquid chlorin is 
now an article of commerce, and large quantities are sold in 
iron cylinders for use in certain processes of extracting gold 
from its ores, and other chemical processes requiring the gas. 

SECTION II.— HYDROCHLORIC ACID 
Symbol HCl. — Molecular Weight 36.5 

122. Occurrence. — This gas is not found free in nature 
except in the gases evolved from certain active volcanoes ; 
its salts, the chlorids, are abundant and important, as was 
stated in the last chapter, and from one of these, viz. 
sodium chlorid, or common salt, nearly all the hydrochloric 
acid of commerce is obtained. 

123. Preparation, (a) By Synthesis. — If equal volumes 
of hydrogen and chlorin be mixed in a flask and exposed to 
the sun, an explosion takes place, and hydrochloric acid is 



94 



CHEMISTRY 



formed. This illustrates the fact that light sometimes aids 
chemical action. 




Fig. 15. 



Caution. — The explosion sometimes breaks the flask, and to pro- 
tect the experimenter from injury a screen of plate glass is usually 
placed in front of it. If a thin-walled flask be used, there is little 
danger of the flying fragments breaking the screen. 

(b) By Burning Hydrogen in Chlorin. 

Hydrochloric acid was prepared synthetically in Experi- 
ment 60, which see. 

(c) By the Action of Sulfuric Acid on Common Scdt. 

Experiment LXIII. — Arrange the apparatus as in Experiment 50. 
With 20 cc. of water in the first bottle, and about 50 cc. in each of the 
others, place 10 grammes common salt in a flask, and when your 
apparatus is all ready, and you are sure that all joints are tight, pour 
into the flask 17 cc. of sulfuric acid diluted with 10 cc. of water. Gas 
is immediately evolved. Heat gradually. Test the gas as follows : — 

1. Hold moist litmus paper in a stream of the gas. Note effect. 
Is the gas visible in the air ? 

2. Prove the solubility of the gas. Is the gas in the flask visible P 



THE CHLORIX FAMILY 95 

3. Does hydrochloric acid burn ? Does it support combustion ? 

4. Pour a few drops of the liquid in the first bottle into about a 
tablespoonful of water, and taste. 

5. Describe the odor. 

6. Drop a piece of zinc in the first bottle. What occurs ? Is 
hydrogen given off ? 

Caution. — The tube which connects the flask with the first bottle 
should not dip beneath the water. In the other bottles the tube by 
which the gas enters should enter the water. Watch the apparatus 
carefully, and prevent the water from running from one bottle into 
another, by raising the stopper of the bottle toward which it is running. 

124. Reactions. — When prepared as above, hydrogen 
sodium sulfate is formed with the following results : — 

Reaction : NaCl + H 2 S0 4 = HC1 + HXaS0 4 . 

If concentrated sulfuric acid be used with an excess of 
salt and a higher temperature maintained, the same weight 
of sulfuric acid will form twice as much hydrochloric acid, 
and the by-product is the normal sodium sulfate instead 
of the hydrogen sodium sulfate. 

2 XaCl + H 2 S0 4 = 2 HC1 + Na 2 SO. 

125. Properties. — Experiment 63 taught us the color, 
odor, solubility, combustibility, and acid reaction of hydro- 
chloric acid gas, and illustrated the use of its aqueous 
solution as a solvent. The dry gas is transparent, but in 
contact with moist air a dense cloud is formed by the 
solution of the gas in an aqueous vapor. At 0° C, water 
dissolves five hundred times its own volume of hydro- 
chloric acid. As the temperature rises, the solubility dimin- 
ishes, so that at 50° C. only 364 volumes will be dissolved. 
The pure gas dissolved in pure water is colorless ; the 
commercial acid, a solution containing about 30% of the 
gas, owes its yellow color to the presence of a small quan- 
tity of iron. 



96 CHEMISTRY 

Hydrochloric acid gas may be liquefied at 10° C. by a 
pressure of forty atmospheres ; the liquid obtained is color- 
less, and is almost without action on metals. The aqueous 
solution of the gas dissolves iron, zinc, and many other 
metals, forming chemical solutions, but it is not as valu- 
able a solvent as nitric acid, which was formerly called 
"Aqua Fortis," or strong water, because of its ability to 
dissolve so many substances. The mixture of nitric and 
hydrochloric acids known as " Aqua Begia," or royal water, 
is a better solvent than either of its components. This 
name was given to it by the alchemists because it dis- 
solves gold, which they considered the king of metals; 
it also dissolves platinum and certain ores, forming chlorids 
of the metals. Its action is due to the nascent chlorin 
evolved when the acids are mixed. 

126. Composition of Hydrochloric Acid. — It has been 

shown that one volume of hydrogen and one volume of 
chlorin combine to form two volumes of hydrochloric acid; 
and since the atomic weight of chlorin is 35.5, it follows 
that 36.5 parts by weight of hydrochloric acid will contain 
35.5 parts of chlorin and one part of hydrogen. 

127. The Manufacture of Hydrochloric Acid. — Large quan- 
tities of hydrochloric acid are now obtained as one of the 
by-products in the Leblanc process of manufacturing soda- 
ash. In the first stage of this process salt is treated with 
sulfuric acid, and heated to convert it into sodium sulfate : 
the hydrochloric acid gas was formerly allowed to escape 
into the atmosphere. The acid-laden atmosphere destroyed 
all vegetable life in the vicinity of the alkali works ; farms 
were rendered worthless, the limestone and metal work 
of buildings was attacked and destroyed, and the death 



THE CHLORIN FAMILY 97 

rate increased. In England the nuisance led to the " Alkali 
Act," which compelled all manufacturers to absorb the 
hydrochloric acid. This is now accomplished by passing 
through tall brick-lined chimneys loosely tilled with coke 
or bricks, and at the top of which a spray of water is 
introduced. The water at the bottom of the chimney is 
nearly saturated with the gas. The commercial acid thus 
prepared is now an important source of income to the 
manufacturer. 

128. Uses. — Hydrochloric acid is extensively used in 
the preparation of ammonium chlorid, and of bleaching 
powder, and is an important reagent in the laboratory. 

SECTION III. — OTHER COMPOUNDS OF CHLORIC 

129. Oxids. — By indirect methods two compounds of 
chlorin and oxygen may be obtained, having the formulas 
C1 2 and C10 2 ; they are very unstable compounds, and 
are, therefore, powerful oxidizing agents, but are of little 
importance. 

130. Acids. — Three acids containing hydrogen, chlorin, 
and oxygen are known : — 

Hypochlorous acid, HC10 
Chloric acid, HC10 3 

Perchloric acid, HC10 4 

These acids are also very unstable, and are good oxidizing 
agents ; they are chiefly important because of the impor- 
tance of their salts, which will be discussed later. 

131. Preparation of the Acids. — If a perchlorate is treated 
with strong sulfuric acid, a sulfate is formed, and perchloric 
acid may be obtained from the solution by distillation. 



9g CHEMISTRY 

When a solution of a chlorate is treated with sulfuric acid, 
chloric acid is liberated, but it cannot be separated from the 
solution by distillation, because decomposition takes place. 
If barium chlorate be used, the sulfate formed is precipi- 
tated and chloric acid is left in solution. 

Hypochlorous acid cannot be obtained in this way, because 
it is decomposed by the stronger acids with the liberation 
of chlorin. It is probable that hypochlorous acid is formed, 
but is at once decomposed by the sulfuric acid. 

132. Formation of Sodium Chlorid by the Action of Hydro- 
chloric Acid on Baking Soda. — If hydrogen sodium carbonate 
(baking soda) is treated with hydrochloric acid, carbon 
dioxid, C0 2 , is given off and common salt is formed. 

HC1 + HNaC0 3 = NaCl + H 2 + C0 2 . 

This reaction is very similar to that which occurs when 
baking powder is moistened, the only difference being that 
rochelle salt is formed by the baking powder instead of 
common salt. It has been suggested that, inasmuch as 
rochelle salt is an injurious ingredient in food, and as 
common salt is commonly used, it would be an improvement 
on existing methods of preparing biscuit, if baking soda and 
hydrochloric acid should be used instead of baking powder. 
There are practical difficulties, however, in determining the 
exact amount of hydrochloric acid to use, and the mistakes 
which would follow its general use would doubtless cause 
serious illnesses. 

SECTION IV. — BROMIN 
Symbol Br. — Atomic Weight 80 

133. Occurrence. — Bromin does not occur free in nature, 
but its compounds, the bromids, are found in small quantities 



THE CHLORIX FAMILY 99 

in sea-water and in the waters of certain salt wells and 
mineral springs. After the extraction of the common salt 
from sea-water, there remains a heavy yellow liquid called 
bittern, which contains sodium and magnesium bromids ; 
this was formerly the principal source from which the 
bromin was obtained, but the bromids are found in larger 
quantities in the upper layers of certain salt deposits, and 
bromin can therefore be prepared more economically from 
these layers than from bittern. 

134. Preparation. — Bromin is prepared by distilling a 
bromid with manganese dioxid and sulfuric acid and con- 
densing the vapor evolved in a well-cooled receiver. It may 
also be prepared by treating a bromid with chlorin. The 
stronger chemical affinity of the chlorin for the metal enables 
the chlorin to decompose the bromid, forming a chlorid and 
setting the bromin free. 

Experiment LXIY. — 1. Examine liquid bromin while contained 
in a bottle ; note its color and odor. (Care.) Is it a mobile or a vis- 
cous liquid? How do you think its density compares with that of 
water ? Pour a few drops into a test tube containing water. Does 
the bromin float on the water or sink ? Does it dissolve in water ? 
Is bromin as soluble as chlorin ? 

2. To one or two cubic centimeters of carbon disulfid in a test tube, 
add a few drops of the water to which bromin was added. What 
color is obtained ? This is the test for free bromin. 

135. Physical Properties. — Bromin is the only non-metal- 
lic element that is a liquid at ordinary temperatures. It is 
volatile and very poisonous, and its vapor is more than five 
times as heavy as air. 

136. Chemical Properties. — Bromin closely resembles 
chlorin in its chemical affinities. It combines directly with 
metals and has a strong affinity for hydrogen. 



100 CHEMISTRY 

137. Uses. — The ease with which it abstracts hydrogen 
from substances leads to its use as a disinfectant and to a 
limited extent as a decolorizer. Its compounds are used in 
medicine and in photography. 

138. Test. — When bromin is dissolved in carbon disulfid, 
an orange liquid is obtained which is characteristic. It also 
turns starch a bright yellow color. 

139. Hydrobromic Acid, HBr. — This acid corresponds to 
hydrochloric acid, which it resembles in its chemical proper- 
ties as well as in composition. 

SECTION V. — IODIN 
Symbol I. — Atomic Weight 127 

140. Occurrence — Like other halogens, iodin occurs in 
nature only in combination. It is found in sea-water, in 
the waters of many mineral springs, and in several impor- 
tant minerals, but the quantity of iodin present in each 
case is exceedingly small. Certain sea-weeds absorb it from 
sea-water, and much of the iodin of commerce is obtained 
from this source, but the dried weeds contain less than one- 
half of 1 % of iodin. The crude sodium nitrate, known as 
Chili saltpetre, contains about 0.2 % of iodin, chiefly as 
sodium iodate. For a number of years the amount of iodin 
obtained from this source exceeded the total consumption 
of the whole world. 

141. Preparation. — Iodin may be prepared by distilling 
a salt containing it with manganese dioxid and sulfuric 
acid, and condensing the vapor in a cooled receiver. A 
solution containing an iodin salt may be obtained by leach- 
ing the ashes of sea-weeds, technically known as kelp; or 
more economically by boiling the sea-weeds with sodium 



THE CHLOEIX FAMILY 101 

carbonate and filtering. The liquid thus obtained contains 
besides the iodin a number of useful substances, which are 
removed by precipitation or crystallization, the iodin salts 
remaining in solution. The solutions obtained by these 
processes are distilled as described above. 

142. Physical Properties. 

Experiment LXV. — 1. Examine iodin crystals, note the color, 
lustre, and general form of the crystals. 

2. Drop a few crystals on a piece of hot sheet iron, holding the 
iron under the hood. 1 Note the color of the vapor. 

3. Drop a crystal of iodin into a test tube containing water. Does 
it dissolve ? Of the three elements chlorin, iodin, and bromin, which 
is most soluble in water ? which least soluble ? which has the greatest 
atomic weight ? which least ? 

4. Drop the smallest particle of iodin that you can pick up on a 
knife blade into a test tube containing carbon disulfid. Note the color 
of the solution. This is often used as a test for free iodin. 

Iodin sublimes slowly at ordinary temperatures, con- 
densing on the side of the bottle containing it which is 
away from the light. At 107° C. it melts, giving off the 
heaviest known vapor. 

143. Chemical Properties. — The chemical affinities of 
iodin are similar to those of chlorin and bromin, but are 
less energetic. 

Starch is turned a dark blue by iodin. 

Experiment LXVL Belatwe Affinity of Chlorin, Iodin, and 
Bromin for Metals. — 1. Pour about 1 cc. of a solution of potassium 
bromid into a test tube containing an equal amount of carbon disulfid ; 
shake the tube. Does bromin in combination change the color of the 
carbon disulfid ? Add a little chlorin water to the mixture, and shake 
the tube to mix the liquids thoroughly. Is there any evidence of free 
chlorin now ? Which has the stronger affinity for potassium, bromin 
or chlorin ? 

1 In laboratories not provided with a hood, it is suggested that the 
teacher perform this experiment, dropping the iodin into a flask and 
heating it 



102 CHEMISTRY 

2. Using a solution of potassium iodid instead of potassium bromid, 
repeat the experiment. Does iodin in combination change the color 
of carbon disulfid ? Does chlorin water set iodin free ? Which has 
the stronger affinity for potassium, iodin or chlorin ? 

3. Pour some bromin water into a solution of potassium iodid con- 
taining some carbon disulfid. Does bromin water set iodin free ? 
Which has the stronger affinity for potassium ? Arrange the three 
elements tested in the order of their affinities for potassium. Also 
arrange them in the order of their atomic weight. Are the lists the 
same ? 

144. Uses. — Dissolved in alcohol it is used in medicine 
as tincture of iodin. Its compounds are used in photography 
and the manufacture of aniline. 

145. Hydriodic Acid, HI. — Corresponds to hydrochloric 
acid. 

SECTION VI.— FLUORIN 

Symbol E. — Atomic Weight 19 

146. Occurrence. — This remarkable element does not 
occur free in nature, and until recently has resisted all 
attempts to isolate it. Its compounds have long been known. 
Fluorspar, the cubical purple crystal occurring in the 
Niagara limestone at Rochester, N.Y., and elsewhere, is 
calcium fluorid, CaF 2 , and cryolite is a double fluorid of 
sodium and aluminum. Fluorin also occurs in the teeth, 
bones, and blood of animals. 

147. Preparation. — Fluorin cannot be prepared by the 
method employed in preparing the other members of this 
family, because of its intense chemical energy. Its com- 
pounds are not easily decomposed, and when the chemist 
succeeds in decomposing one of them the liberated fluorin 
usually forms a new compound with some element. It has, 
in many experiments, combined with the material of the 
vessel in which it was separated. Gold, platinum, glass, and 



THE CHLORIN FAMILY 103 

carbon vessels have been tried, but in each case a fluoric! 
was obtained instead of the element. In 1886, Moissan 
solved the problem by electrolyzing a solution of the acid 
potassium fluoric! in anhydrous hydrofluoric acid in a U-tube 
made of an alloy of platinum and iridium. 

148. Physical Properties. — Fluorin is a pale yellow- 
green gas about 1J times heavier than air. Its odor is not 
definitely known, as it attacks the mucous membranes. 
Its solubility in water is unknown, for it decomposes water, 
forming hydrofluoric acid, HF. 

149. Chemical Properties. — Fluorin combines with metals, 
heat and light being developed in some cases ; in contact 
with hydrogen it at once explodes ; iodin, sulfur, and phos- 
phorus melt and burst into flame in fluorin; silicon takes 
fire and burns with great brilliancy, and organic compounds 
are quickly destroyed in the gas. 

150. Hydrofluoric Acid, HF. — This powerful acid is a 
colorless, fuming liquid which must be handled with the 
greatest care. Inhaled in a pure state, it causes death, and 
even when greatly diluted with air, irritates the respiratory 
organs. A single drop on the skin produces ulcerated sores, 
accompanied by aching pains throughout the whole body. 
It has a strong affinity for water, and mixed with it has the 
power of dissolving glass. The dry gas does not attack 
glass, the slightest trace of moisture being necessary. The 
commercial acid is a solution in water, and is largely used 
for etching designs on glass and for etching the graduations 
upon measuring glasses, thermometers, etc. It must be 
kept in gutta percha or wax bottles. The hydrofluoric acid 
of commerce is prepared by distilling fluorspar and sulfuric 
acid in leaden retorts and dissolving the vapor in water 
contained in a series of leaden bottles. 



104 CHEMISTRY 

151. Process of Etching Glass. 

Experiment LXVII. — Let each student provide himself with a 
glass slip such as is used for microscope slides. 

1. Coat the glass with wax by dipping it in a dish containing 
melted beeswax (not too hot) , and holding it horizontally while the 
wax cools. 

2. Write on the slip with a hat pin, being careful to cut through the 
wax. The instructor will place a leaden tray under the hood and pour 
into it a small amount of commercial hydrofluoric acid and an equal 
quantity of water. 

3. Place the slip in the tray, engraved side downward ; allow it to 
remain five minutes. Remove the slip with a pair of crucible tongs, 
dropping it into a basin of water. 

4. Remove the wax with a knife and wash the slip with benzine. 
If a large piece of glass is to be etched, the following process is 
preferred. It is quite easy by the following process to etch a large 
pane of glass with some appropriate design which provides places for 
the autograph of the members of the class. 

Experiment LXVIII. Alternate. — 1. Apply a coat of asphaltum 
varnish to the article to be etched. When dry, hold it to the light and 
touch up any air bubbles. 

2. Draw the desired design on paper, sprinkle the asphaltum rather 
thickly with minium, fasten the corners of the design securely to the 
glass with mucilage. Trace the design with a stylus, using slight 
pressure ; this will cause the minium to adhere to the asphaltum where 
the stylus has pressed it, and on removing the paper and dusting off 
the minium the design will be found on the asphaltum in red lines. 

3. Cut each line through the asphaltum, using a stylus or a hat pin. 

4. Pour strong hydrofluoric acid on the design, allowing it to 
remain for several minutes. Wash the glass with water and remove 
the asphaltum with turpentine. 

The glass is dissolved by the hydrofluoric acid, and a deep 
line will be cut wherever the asphaltum has been removed. 
If the glass has the formula CaSi0 3 , the reaction is as 
follows : — 

CaSi0 3 + 6 HF = CaF 2 + SiF 4 + 3 H 2 0. 



THE CHLORIN FAMILY 



105 



152. Properties of the Elements of the Chlorin Family. — 

The compounds of the members of this family resemble 
each other in the shape of their crystals, in their chemical 
properties, and in their composition. The properties of the 
elements seem to depend upon their atomic weight as shown 
by the following table : — 





Atomic 
Weight 


State 


Color of Vapor 


Chemical 
Activity 


Solubility 


Fluorin 
Chlorin 
Bromin 
lodin 


19 
35.5 

80 
127 


Gas 
Gas 
Liquid 
Solid 


Almost colorless 
Green-yellow 
Red-brown 
Violet 


- 


- 



It will be observed that as the atomic weight increases, 
the density and depth of color of the vapor increase. Fill 
the blank spaces in the two right-hand columns. 



REVIEW QUESTIONS 

1. Describe the process and state the theory of bleaching with 
chlorin. 

2. From what is chlorin chiefly obtainable? What property of 
chlorin renders it valuable in the arts ? 

3. Describe the preparation of chlorin from hydrochloric acid. 

4. If chlorin and hydrogen are mixed and exposed to sunlight, 
what takes place ? What is the product called ? What proportions, 
by volume, of chlorin and hydrogen enter into it ? What proportions 
by weight ? 

5. Describe two methods of preparing chlorin. Describe an ex- 
periment illustrating the affinity of chlorin for metals. 

6. Tell what you can of hydrochloric acid as to its manufacture, 
properties, and uses. 

7. In what important acid is chlorin an element ? How does this 
acid affect many of the metals ? 

8. Describe the formation of sodium chlorid by the action of 
hydrochloric acid on baking soda. 



106 CHEMISTRY 

9. What is aqua regia ? 

10. How did you prove that hydrochloric acid gas was soluble in 
water ? 

11. State the occurrence, properties of fluorin. 

12. What difficulties prevent its easy preparation ? 

13. State the properties of hydrofluoric acid. 

14. Describe a process of etching glass. 

15. Judging from its atomic weight, how would you expect the 
chemical activity of fluorin to compare with that of the other halogens ? 

16. How should its solubility in water compare with the others ? 

17. Discuss the physical properties of chlorin as follows : (a) color, 
(b) odor, (c) weight. 

18. Discuss chemical properties of chlorin as follows : (a) chemical 
energy, (6) special affinities, (c) relation to combustion, (d) affinities 
for hydrogen and carbon. 

19. Describe the effect of iodin on the skin. 



CHAPTER XV 
SULFUR AND ITS COMPOUNDS 

SECTION L — SULFUR 
Symbol S. — Atomic Weight 32 

153. Occurrence. — In the free state, sulfur is found chiefly 
in volcanic districts. In this country important deposits 
are found in California, and in the lava-covered regions of 
the eastern slope of the Rocky Mountains, particularly in 
Humboldt County, Nevada. There are also large deposits 
in Italy, Sicily, Iceland, China, and India. Combined with 
hydrogen, it occurs in many springs. In combination with 
metals as sulficls and sulfates, it occurs in enormous quanti- 
ties in all parts of the world. Many important ores are sul- 
fids, for example, galena or lead sulfid; cinnabar or mercury 
sulfid ; zinc blends or zinc sulfid ; realgar or arsenic sulfid, 
etc. Gypsum and heavy spar are sulfates. 

154. Extraction of Sulfur from its Ores. — Native sulfur 
is usually mixed with earthy or mineral substances, from 
which it is separated by igniting a part of the sulfur in a 
limited supply of air; the heat of the burning sulfur melts 
the rest of the sulfur which is drawn off. In the larger 
establishments this is conducted in brick kilns with slop- 
ing bottoms, in which the melted sulfur is collected. Some- 
times the ore is piled up and covered with earth to exclude 
the air, and the pile is ignited, and the sulfur settles to the 

107 



108 CHEMISTRY 

bottom of the pile and runs out through channels dug in 
the ground. This method is extremely wasteful. Large 
quantities of sulfur are now obtained as by-products in the 
process of smelting copper pyrites, of making illuminating 
gas, and in the Leblanc process of making soda ash. 

155. Refining Sulfur. — The crude sulfur obtained by the 
above processes is refined by distilling it in earthenware 
retorts and condensing the vapor in brick chambers ; if the 
temperature of the condensing chamber is below the melting 
point of sulfur, the vapor is deposited as a fine powder con- 
sisting of minute granules and known in commerce as 
" flowers of sulfur " ; if the temperature is above the melting 
point, the vapor collects on the floor of the room in a liquid 
state. This is drawn off and cast into large cakes or 
cylindrical rods, the latter form being known as the roll 
brimstone in commerce. 

156. Milk of Sulfur. — A third commercial form, called 
"lac sulfur," is obtained by precipitation from solution. 
It is somewhat lighter in color than the other commercial 
forms and usually contains calcium salts in considerable 
quantity. It is found in nature as a white deposit at the 
bottom of sulfur springs. 

157. Behavior of Sulfur at Different Temperatures. — At 
— 50° C. sulfur is almost colorless; at ordinary temperature 
it is a yellow, brittle, crystalline solid; as the temperature 
is increased a change occurs at 114° C, another between 
114° C. and 150° C, a third at 230° C, a fourth between 
300° C. and 400° C, and at 448° C. it boils. 

Experiment LXIX. — Heat a few grammes of sulfur in a dry test 
tube. Apply the heat very slowly ami describe all changes of color or 
density which occur. What is the color of the vapor ? 



SULFUR AND ITS COMPOUNDS 109 

158. The Allotropic Forms of Sulfur. — Allotropism is the 
property certain substances have of existing in two or more 
conditions which are distinct in their physical or chemical 
relations. 

Experiment LXX. Prismatic Sulfur. Crystallization by Fusion. — 
Melt a few grainmes of sulfur in a test tube, being careful that it does 
not change color. Pour it into a piece of paper folded as for filtering ; 
as the crystals begin to form, unfold the paper and hold it vertically 
until the liquid sulfur drains from the crystals. Examine the crystals 
with a lens. Describe them. Are they soluble in carbon disulfid ? 

This form is not permanent, but passes slowly into the 
octohedral form. Its specific gravity is 1.96, a little less 
than that of the next variety. 

Experiment L XXI. Octahedral or Bhombic Sulfur. Crystallization 
from Solution. — Place half a gramme on a filter paper, pour a little 
carbon disulfid through the filter into a test bottle ; when it is filtered, 
set the bottle aside for a few hours. Describe the crystals which are 
found in the bottle after the carbon disulfid has evaporated. 

This is the most stable form, and therefore the form 
which occurs in nature ; its specific gravity is 2.05. 

Experiment LXXII. Plastic Sulfur. — Heat a few grammes of 
sulfur in a test tube until it boils, then pour it into a dish of water. 
Examine it carefully and describe its properties. 

Plastic sulfur is not permanent in air, but changes to 
the octohedral form in a day or so; its specific gravity 
is 1.96. Is it soluble in carbon disulfid ? 

A fourth form is a white amorphous substance forming 
about 5 % of flowers of sulfur, from which it may be sepa- 
rated by dissolving the crystals in carbon disulfid, in which 
the white amorphous sulfur is insoluble. 

Experiment LXXIII. — Examine the forms of sulfur which you 
have prepared, describe their physical properties, ignite a piece of each, 
observe the character of the flame and the odor of the gas formed by 
the combustion of each. What evidence do you obtain that sulfur is 
allotropic ? 



HO CHEMISTRY 

There are several other allotropic forms, but they are of 
minor importance; the differences between them may be 
attributed to the varying number of atoms in the molecule. 

159. Properties. — We have learned some of the more 
important properties of sulfur from the preceding experi- 
ments, but the following additional properties must not be 
overlooked : — 

(a) It is insoluble in water. 

(b) At high temperatures it has a strong affinity for 
oxygen. 

At ordinary temperatures sulfur does not combine with 
oxygen. When heated to about 260° C. it burns actively and 
forms sulfur dioxid, S0 2 . When one attempts to light it 
with a match, they will observe that the time required to 
ignite it depends upon the quantity of sulfur that must be 
raised to the kindling temperature. 

(c) Its affinity for metals. 

Experiment LXXIV. — Heat a few grammes of sulfur to boiling ; 
hold a spiral of fine copper wire so that the end just dips in the boil- 
ing sulfur. What evidence of chemical action do you observe? Is 
the wire changed in appearance ? Is it still pure copper ? Test its 
brittleness and other physical properties. 

The great affinity of sulfur for metal is shown by the 
large number of sulfids found in nature, and also by the 
activity with which it combines with metals, the union in 
many cases developing heat and light, as in Experiment 19. 

160. Uses. — Sulfur is extensively used in manufacturing 
certain substances, among which we may mention gun- 
powder, fireworks, matches, and sulfuric acid ; it is also 
used in the process of vulcanizing caoutchouc, and in the 
preparation of sulfur dioxid for bleaching and disinfecting. 



SULFUR AND ITS COMPOUNDS HI 

161. Its Use in Making Lucifer Matches. — The low 

kindling temperature of sulfur, 260° C, is advantageously 
applied in making matches. The small amount of phos- 
phorus on the end of the match stick could not raise the 
wood to its kindling temperature, but it easily raises sulfur 
to 260° C, and the heat of the burning sulfur ignites the 
wood. In certain kinds of matches paraffin is used for this 
purpose instead of sulfur, because of the disagreeable odor 
of burning sulfur. 

TJie common sulfur match is prepared as follows: The 
match sticks are clipped in melted sulfur to a depth of 
about half an inch, and afterward tipped with an emulsion 
of the following substances : — 

Ordinary phosphorus 9 parts 

Saltpetre 14 " 

Manganese dioxid 14 " 

Glue 16 " 

SECTION II. — SULFUR DIOXID 

Formula SOo. — Molecular Weight 64 

162. Occurrence. — This substance exists in the gases 
evolved by volcanoes, and in solution in the springs of cer- 
tain volcanic regions. It is one of the constituents of coal 
gas, and is usually present in the air of cities. 

163. Preparation. — Sulfur dioxid is formed when sulfur 
is burned in air or in oxygen, and for many purposes is best 
prepared in this way. For experimental purposes the fol- 
lowing method is preferred : — 

Experiment LXXV. — In a flask place six or eight pieces of sheet 
copper. Pour 5 or 10 cc. of concentrated H2SO4 over it. Arrange 
the apparatus for collecting gas over water. Heat gently and can- 



112 CHEMISTRY 

tiously. The moment the gas begins to come off, lower the flame, and 
keep it at such a height that the evolution is regular and not too rapid. 
After concluding whether or not the gas is soluble in water, collect a 
bottle by downward displacement. It is more than twice as heavy as 
air. Determine whether the gas will burn or support combustion. 
What effect has the solution of the gas on litmus paper ? Allow the 
gas to bubble through a solution of potassium permanganate, a solu- 
tion of chromic acid, a solution of iodin. What effect has the gas on 
the color of the solution ? Note the physical properties of the gas. 

The relation between the factors and the products in this 
reaction is shown by the following equation : — 

Cu + 2 H 2 SO, = CuS0 4 + 2 HoO + S0 2 . 

It is probable, however, that the copper acts upon a 
molecule of the acid, and that the nascent hydrogen reduces 
the second molecule of the acid, as was explained in Ex- 
periment 57, in which copper apparently reduced nitric 
acid. 

164. Properties. — At ordinary pressure sulfur dioxid is 
condensed to a liquid at — 10° C. If the gas be passed 
through a tube packed in ice and salt, it is liquefied at 
ordinary pressure. At ordinary temperatures it liquefies 
under a pressure of 75 pounds per square inch. The sudden 
evaporation of liquid sulfur dioxid causes intense cold, and 
the liquid is often used as a refrigerating agent. Sulfur 
dioxid is irrespirable and perhaps poisonous. It destroys 
certain kinds of germs, particularly those which cause fer- 
mentation and decay of organic substances. Its effect on 
disease germs is very much overestimated, but when used 
in large quantity it is a valuable disinfectant. Sulfur 
dioxid combines with water to form sulfurous acid, H 2 S0 3 , 
which has a strong affinity for oxygen, and which takes it 
from many substances. In certain cases sulfur dioxid is 
said to bleach moist substances by abstracting the oxygen 



SULFUR AND ITS COMPOUNDS 113 

from the water, the nascent hydrogen reducing the coloring 
matter, a process which is the reverse of that by which 
chlorin destroys color. In other cases the bleaching action 
is due to the formation of a colorless compound by the 
sulfur dioxid and the pigment, and in such cases the color 
may be restored by any chemical which will decompose the 
compound formed. The yellow color which flannel gradu- 
ally acquires when washed with soap is an illustration of 
the power of alkalies to restore the original color of sub- 
stances bleached with sulfur dioxid. 

165. Uses. — It is extensively used in bleaching straw, 
silk, and woollen goods, or any material that would be in- 
jured by chlorin. There are two processes : — 

First. — By suspending the article to be bleached in the 
fumes of burning sulfur. 

Second. — By immersing the substance in an aqueous 
solution of the gas. 

Experiment LXXVI. — Suspend a colored flower in a bell jar and 
burn sulfur under it. After the flower is bleached, dip it into dilute 
sulfuric acid. What occurs ? 

As sulfur dioxid prevents fermentation, it is sometimes 
used in preserving fruit juice. The juices are treated with 
some substance that gives off the gas slowly, e.g. any sulfite. 

Note. — The writer is unable to see why a substance which will 
prevent fermentation in the air should not prevent fermentation in 
the stomach, or digestion, thus rendering the articles of food preserved 
in this way worse than useless. 

Sulfur dioxid is sometimes used to extinguish fires in 
closed rooms or chimneys. If sulfur is thrown on the fire, 
it is ignited, using up the oxygen and filling the space with 
a non-supporter of combustion. 



114 CHEMISTRY 

Liquid sulfur clioxid produces intense cold if rapidly 
evaporated, and is sometimes used for freezing purposes; 
it is also extensively used as a disinfectant, in the manu- 
facture of sulfuric acid, and as an antichlor in paper mills. 



SECTION III. — HYDROGEN SULFID 
Formula H 2 S. — Molecular Weight 34 

166. Occurrence. — This compound issues from the earth 
in volcanic regions ; decomposing organic substances con- 
taining sulfur evolve it, and the water of sulfur springs 
owes its characteristic properties to the dissolved hydrogen 
sulfid present. 

167. Preparation. — (a) Hydrogen sulfid may be formed 
by synthesis, by passing streams of hydrogen and sulfur 
vapor through a hot porcelain tube, (b) In the laboratory 
it is usually prepared by decomposing a sulfid with an acid. 

Experiment L XXVII. — 1. Arrange your apparatus as for prepa- 
ration of hydrogen, page 42. 

2. Place a few grains of iron sulfid in the generating bottle and 
cover it with dilute sulfuric acid. Collect two bottles of the gas over 
water ; test the water with litmus paper. 

3. Is the gas soluble in water ? 

4. Determine whether the gas should be collected by upward or 
downward displacement, and fill three bottles. 

5. Is the gas combustible or a supporter of combustion ? 

6. Devise a test which will show whether the gas is explosive when 
mixed with air. 

7. Apply a lighted match to the mouth of a bottle of the gas, and 
look for evidence of the formation of water, or sulfur dioxid, or both. 
Which element of the hydrogen sulfid is deposited on the sides of the 
bottle ? 

8. Pass H 2 S successively through solutions containing lead nitrate, 
zinc sulfate, copper sulfate, cadmium chlorid, and arsenic chlorid. 
What do you observe in each case ? The substances formed are re- 



SULFUR AND ITS COMPOUNDS 115 

spectively the sulfids of lead, zinc, copper, cadmium, and arsenic. 
The reaction in the case of copper sulfate is as follows : — 

C11SO4 + H 2 S = CuS + H2SO4. 

9. Describe the odor of the gas and the character of its flame. 
When hydrogen sulfid is prepared by treating iron sulfid with sulfuric 
acid the following reaction occurs : — 

FeS + H 2 S0 4 = FeS0 4 + H 2 S. 

168. Properties. — Hydrogen sulfid is a powerful poison. 
In an abundant quantity of air it burns, forming sulfur 
dioxid and water. When the supply of oxygen is limited 
one of the elements is not completely consumed, as was 
shown in Experiment 77. At ordinary pressures, hydrogen 
sulfid is liquefied at — 62° C. ; at ordinary temperatures it 
also liquefies when subjected to a pressure of about seven- 
teen atmospheres. The acid reaction of the aqueous solu- 
tion of hydrogen sulfid has led chemists to consider it an 
acid, and it is often called hydrosulfuric acid ; the sulfids 
are considered its salts. Hydrogen sulfid is very unstable ; 
at a temperature slightly above 400° C. its molecule is 
broken up ; it is decomposed by all of the halogens ; many 
metals act upon it at ordinary temperatures, replacing its 
hydrogen and forming sulfids. Because of its instability, 
hydrogen sulfid often acts as an excellent reducing agent, 
its efficiency being due to the action of nascent hydrogen. 

169. Uses. — Hydrogen sulfid is extensively used in 
chemical analysis. When a solution containing certain 
basic elements is treated with this gas, a sulfid is formed 
which may be recognized by its color, or by its behavior 
when treated with certain solvents. Several sulfids are in- 
soluble in an acid solution, and are, therefore, deposited as 
solids, or precipitated, when gas is passed into an acid solu- 
tion containing them. Others are soluble in an acid, but 



11(3 CHEMISTRY 

insoluble in an alkaline solution, and are therefore precipi- 
tated from alkaline solutions. Still others are soluble in 
water, and remain in solution. These properties form the 
basis of the system of qualitative analysis generally used. 

170. Test. — (a) For Hydrogen Sulfid. 

1. The free gas may be detected by its odor. 

2. A piece of filter paper moistened with lead acetate is 
blackened by the gas. 

(b) For Sulfids. 

1. Sulfids are decomposed by hydrochloric acid, with 
evolution of hydrogen sulfid, which may be recognized as 
in (a). 

2. Pulverize the substance to be tested, mix with sodium 
carbonate, Na 2 C0 3 , on a bit of porcelain or platinum foil, 
and fuse it in the Bunsen flame. Place the fused mass on 
a clean silver coin and add a drop of water. If a sulfid be 
present, a black spot will appear on the silver. Silver is 
blackened by vulcanized rubber and by eggs. What does 
this indicate? 

SECTION IV. — SULFURIC ACID 

(OIL OF VITRIOL) 

Formula H 2 S0 4 . — Molecular Weight 98 

171. Occurrence. — Small quantities of sulfuric acid are 
found in some rivers and springs in volcanic regions; its 
salts are quite abundant. 

172. Preparation. — Sulfuric acid cannot be easily pre- 
pared from its salts, but is manufactured on a large scale 
by oxidizing sulfurous acid ; the chemical changes involved 
in the process are rudely illustrated in the following experi- 
ment. 



SULFUR AND ITS COMPOUNDS 117 

Experiment LXXYIII. — Pour water into your largest bottle to a 
depth of about one inch, lower burning sulfur into the bottle, using an 
ignition spoon ; cover the bottle with a glass plate. After the sulfur 
is extinguished, stir the sulfur dioxid in the bottle with a glass rod 
dipped in nitric acid. Is there any evidence of the formation of nitro- 
gen peroxid ? Of nitric oxid ? When the sulfur dioxid has changed 
color, cover the bottle with the hand and shake it, dissolving the gases. 
Repeat the process three times over the same layer of water ; bring a 
sample of the sulfuric acid thus formed to the desk to be tested. 

173. The Chemical Changes involved in this process are 
indicated in the following reactions : — 

S0 2 +H 2 = H 2 S0 3 , 

H 2 S0 3 + = H 2 S0 4 . 

Nitric acid is used to hasten this oxidation of the sul- 
furons acid, which takes place very slowly in air ; its action 
is represented thus : — 

2 HN0 3 + 3 S0 2 + 2 H 2 = 3 H 2 S0 4 + 2 NO. 

Nitric acid is much more expensive than sulfuric, and if it 
were not for the interesting action of the nitric oxid formed 
in the last reaction, nitric acid could not be used for this 
purpose. It will be remembered that nitric oxid takes 
oxygen from the air, forming nitrogen peroxid, and that 
nitrogen peroxid is an excellent oxidizing agent. The nitro- 
gen peroxid converts another molecule of sulfurous acid into 
sulfuric acid, and is again reduced to nitric oxid thus : — 

NO + = N0 2 , 

NO, + H 2 S0 3 = H 2 S0 4 + NO. 

The nitric oxid therefore acts as a carrier of oxygen from 
the air to the sulfurous acid, alternately abstracting it from 
the air and giving it up to the sulfurous acid ; theoretically 



118 CHEMISTRY 

there is no limit to the number of molecules of sulfurous acid 
that may be oxidized by a single molecule of nitric oxid. 

174. Manufacture of Sulfuric Acid. — On a manufacturing 
scale this reaction is carried on in lead-lined chambers 
usually about 100 feet long, 20 feet wide, and 20 feet high, 
several of these chambers being connected so that the gases 
may pass from one to another. Lead is selected for this 
purpose because dilute sulfuric acid does not dissolve it. 
No other metals can be used with the lead, as electric action 
would ensue, and one of the metals would be dissolved. 
The leaden chamber must therefore be lined without solder 
and without nails; the sheets of lead are joined by melting 
the edges with an oxyhydrogen blowpipe and are supported 
by straps of lead fastened to the outside of the lining. 

At one end of a series of such chambers are furnaces in 
which sulfur dioxid is formed by burning sulfur or iron 
pyrites in a supply of air which is carefully controlled to 
prevent too great dilution of the gases or too small a supply 
of oxygen. The gas from these furnaces heats the "nitre 
pots," or vessels containing potassium nitrate and sulfuric 
acid, which form nitric acid. From this point, the air, 
sulfur dioxid, and nitric acid are conducted to the leaden 
chambers. Jets of steam pour into the chambers at frequent 
intervals. At the end of the last chamber of the series is 
a leaden tower filled with coke ; a spray of strong sulfuric 
acid flows in at the top of this tower and absorbs nitrogen 
peroxid and returns it to the chamber. From this tower 
the gases pass into a tall chimney which creates a strong 
draft and causes the circulation of the gases within the 
chamber. 

The acid formed is collected on the floor of the chamber, 
and is removed when rather dilute, as the strong acid dis- 



SULFUR AND ITS COMPOUNDS 119 

solves the lead. It is then heated in glass or platinum 
stills until it contains only two per cent of water, when it 
is ready for the consumer. 

. 175. Properties. — (a) At ordinary temperature pure sul- 
furic acid is a colorless, oily liquid 1.8 times heavier than 
water. At 10.5° C. it freezes, (b) It has a marked affinity 
for water ; when mixed with it much heat is evolved, and 
a contraction in volume takes place. Sulfuric acid does not 
evaporate at ordinary temperatures, but absorbs moisture 
from the air, increasing in volume quite rapidly in moist 
weather unless kept in tightly stoppered bottles. Many 
organic substances containing hydrogen and oxygen are 
decomposed by sulfuric acid, these elements being extracted 
in the proportions in which they form water. Experiment 2 
illustrates this fact. Wood is charred by the acid, because 
it loses its hydrogen and oxygen, (c) Sulfuric acid forms 
several definite compounds with water, the greatest amount 
of heat being developed when two molecules of water com- 
bine with one of sulfuric acid, (cl) At high temperatures 
sulfuric acid forms more stable compounds with the bases 
than most other acids, and therefore when sulfuric acid is 
heated with a salt, a sulfate is formed and the acid which 
the salt contained is liberated. Nearly all processes of 
preparing acids are based upon this ability of sulfuric acid 
to decompose salts. 

176. Uses. — Sulfuric acid is our most important reagent. 
Most chemical industries depend upon it ; e.g. the refining 
of petroleum, also the manufacture of artificial fertilizers, 
phosphorus, sodium carbonate, and alum. In the laboratory 
it is used for drying gases, in the preparation of most acids, 
and in many other reactions with several of which the 
student is already familiar. 



120 CHEMISTRY 



REVIEW QUESTIONS 

1. In what four allotropic forms does sulfur occur ? What does 
allotropic mean ? 

2. In what forms is sulfur known in commerce ? 

3. State the color, odor, weight, and state of sulfur dioxid. 

4. Describe the extraction of sulfur from its ores, and discuss its 
behavior at different temperatures. 

5. Compare the crystals of sulfur formed by solution with the 
crystals of sulfur formed by fusion. 

6. Describe the manufacture of matches. 

7. Describe the preparation of hydrogen sulfid. Give equation. 

8. For what is hydrogen sulfid used in the chemical laboratory ? 
Discuss its instability. 

9. What inorganic substance is found in vulcanized rubber ? How 
may the rubber be tested for its presence ? 

10. Describe the manufacture of sulfuric acid ; write the reactions 
which take place, and give its uses. 

11. For what purpose is nitric acid used in the manufacture of 
sulfuric acid ? 

12. Describe the method of preparing sulfur dioxid from sulfuric 
acid. State two purposes for which sulfur dioxid is used in large 
quantities. 



CHAPTER XVI 
CERTAIN CHEMICAL RELATIONS 

177. Basicity of Acids. — An acid which, contains only 
one replaceable hydrogen atom is said to be monobasic. 
Hydrochloric and nitric acids belong to this class. 

An acid which contains two replaceable hydrogen atoms is 
said to be dibasic. Sulfuric acid, H 2 SO^ and carbonic acid, 
H 2 C0 3 , belong to this class. The terms tribasic, tetrabasic, 
etc., are applied to acids having three, four, etc., replaceable 
hydrogen atoms. 

A dibasic acid may form a compound with certain basic 
elements like sodium, in which only one of the hydrogen 
atoms is replaced; the salt thus formed frequently reddens 
blue litmus paper and has the power to neutralize more of 
the basic element ; as it retains some of the properties of 
the acid* it is called an acid salt. The salt formed when 
both of the hydrogen atoms are replaced is an entirely dis- 
tinct substance and is called a normal salt. Hydrochloric 
and nitric acids can form but one salt with a given element, 
but the dibasic acids may form two salts with a single 
metal as is illustrated below: — 

ACID SALTS 

Potassium acid sulfate, HKS0 4 

Sodium acid sulfate, HjSTaS0 4 

Potassium acid carbonate (saleratus), HKC0 3 
Sodium acid carbonate (baking soda), HN"aC0 3 
121 



122 



CHEMISTRY 



NORMAL SALTS 

Potassium sulfate, K 2 S0 4 

Sodium sulfate, Na^SC^ 

Sodium carbonate (washing soda), Na 2 C0 3 

Potassium carbonate (pearl-ash), K 2 C0 3 

Acids of higher basicity also form both acid and normal 
salts. 

An acid salt is one that contains replaceable hydrogen. 

A normal salt is one in ivhich the whole of the replaceable 
hydrogen has been replaced by the base. 

178. The Theory of Valence. — Considering the formulas 
of the binary compounds of hydrogen, we observe that the 
elements differ in respect to the number of atoms of hydro- 
gen with which they combine, and that they may be ar- 
ranged in classes upon this basis. The following formulas 
illustrate this fact : — 



I 


II 


ill 


IV 


HF 


H 2 


NH 3 


CH 4 


HC1 


H 2 S 


PH 3 


*SiH 4 


HBr 


H 2 Se 


AsH 3 




HI 









The formulas of the chlorids show a similar difference 
in the number of atoms of the hydrogen of hydrochloric 
acid which the elements can replace, thus : — 





1 


II 


in 


IV 


V 


NaCl 
KC1 

AgCl 


CaCl 2 
BaCl 2 
ZnCla 


BiCl 3 
SbCl 3 


SnCU 

CC1 4 


FCI5 





CERTAIN CHEMICAL RELATIONS 



123 



Tlie ability of an element to combine with or replace hydro- 
gen is called valence. 

Elements are said to be univalent, bivalent, trivalent, etc., 
as they combine with or replace one, two, three, etc., atoms 
of hydrogen. 

The terms monad, dyad, and triad are sometimes used 
instead of univalent, bivalent, and trivalent, but the latter 
terms are to be preferred. 

Valence of the Elements 



Unii 


^alent 


Bivalent 


Trivalent 


Quadrivalent 


F 


19 


16 


Sb 120 


Al 27 


CI 


35.5 


S 32 


As 75 


C 12 


Br 


80 


Ca 40 


Bi 208 


Cr 52 


I 


127 


Sr 87.5 


B 11 




H 


1 


Ba 137 


P 31 




Na 


23 


Cd 112 


N 14 




K 


39 


Fe 56 






Li 


7 


63 






Ag 


108 


Sn 118 






Ail 


186 


Zn 65 
Hg 200 







The valence of an element is often indicated by Roman 
numerals written above the symbol to the right, thus : — 

Fe^ indicates quadrivalent iron. Valence may also be 
indicated in graphic formula by the number of lines drawn 
to a symbol, thus, CH 4 may be written : — 



H— C— H, and H,0 becomes H— O— H. 

I 
H 

Although the valence of many of the elements appears 



124 CHEMISTRY 

to be variable, the classification is of great assistance in 
writing the formulas of the common compounds. Thus, if 
one desires to write the formula of the sulfate of a univa- 
lent element, he knows that there must be as many atoms 
of the element as there are atoms of hydrogen in sulfuric 
acid; i.e. he considers that the sulfate is formed by re- 
placing the hydrogen of the acid with the given element. 
Potassium sulphate, K 2 S0 4 , may be taken as a type of the 
sulfates of univalent metals ; calcium sulfate, CaS0 4 , as 
a type of the sulfates of bivalent metals ; and antimony 
sulfate, Sb 2 (S0 4 ) 3 , of trivalent metals. 

179. The Nascent State. 

The term nascent state is convenient, but is not very accurate, 
because it implies that the substance to which it is applied has been 
liberated from some compound, and exists in some unusual form or 
state in which it possesses unusual chemical energy, whereas the 
nascent element does not exist in the free state at all, but passes 
directly from the molecule of the factor to that of the product. The 
lesser chemical energy in its normal state is, no doubt, due to the 
fact that two or more atoms of the element are united to form a 
molecule, and, whatever the nature of the force which holds them 
together, energy must be expended to overcome it before the atoms 
can form new combinations. Now, in the case of the so-called nascent 
element it will be seen that the chemical change involves at least 
three molecules, that one of these molecules has the power to decom- 
pose a second molecule and replace some of its atoms, and that the 
third molecule is, therefore, acted upon by the full chemical energy 
of the nascent atom. 

The following diagrams will assist the student to understand the 
increased chemical activity of nascent hydrogen. An atom of copper 
has the power to displace the hydrogen of two molecules of the 
acid forming copper nitrate, Cu(X0 3 ) 2 . The copper atom attracts 
the NO3 group of atoms, and then hydrogen is at the same time 
attracted by the HO group of a neighboring molecule of nitric acid, 
and, under the action of these forces, a rearrangement of the atoms is 
effected, forming, at the same instant, molecules of copper nitrate, 
water, and nitrogen peroxid. 






CERTAIN CHEMICAL RELATIONS 125 



HO . N0 2 



X H.N0 3 



> 



H.NOs 
HO . N0 2 

If hydrogen gas be passed through nitric acid, the case is quite 
different. The hydrogen atoms are held together by a certain force, 
and the HO group is held to the N0 2 group. The attraction between 
the atom of hydrogen and the HO group is not great enough to over- 
come the attraction between the hydrogen atoms and to separate the 
HO and the NO2 groups at the same time. 

HO.NO2 HO.N0 2 

V/ 

In the nascent state, then, monatomic elements should not show 
increased activity, while all others should. 

180. Avogadro's Law. — An Italian physicist named Avo- 
gadrOj who had been studying the specific gravities of aeri- 
form bodies, in 1811 announced his belief that under like 
conditions of temperature and pressure equal volumes of all 
gases, icJiether simple or compound, contain the same number 
of molecules. Although this important law was not at once 
accepted, it can now be shown mathematically that in order 
that equal volumes of gases may expand and contract 
equally under like changes of temperature or pressure, it 
is necessary that each volume contain the same number 
of molecules. 

181. Some Deductions from Avogadro's Law. — 1. It will 
be observed that the vapor densities and the atomic weights 
of the first nine elements in the following table are numeri- 
cally equal. There are, therefore, in equal volumes of these 
elements the same number of atoms, and as there are also 



126 



CHEMISTRY 



the same number of molecules in the equal volumes, it 
follows that there must be the same number of atoms in each 
molecule of each of the nine elements. 

Table of Vapor Densities and Atomic Weights 





Elements 




Atomic 
Weight 


Molecular 
Weight 


Vapor 
Density 


Hydrogen 

Nitrogen 


1 

14 
16 
19 
32 
35.5 
79 
80 
127 


2 

28 

32 

38 

64 

71 

158 

180 

254 


1 
14 
16 


Fluorin 

Sulfur 


19 
32 


Chlorin 

Selenium 

Bromin 

Iodin 


35.5 
79 
80 
127 


Sodium 

Potassium 

Zinc 

Cadmium 

Mercury 


23 
39 
65 
112 
200 
31 
75 


23 
39 
65 
112 
200 
124 
300 


11.5 
19.5 
32.5 
56 
100 
62 


Arsenic 


150 


Compounds 




Molecular 
Weight 


Vapor 
Density 


Water, H 2 

Hydrochloric acid, HC1 

Hydriodic acid, HI 


18 
36.5 
81 
128 
17 
28 
44 
44 


9 

18.25 
40.5 
64 

8.5 


Carbon monoxid, CO 

Carbon dioxid, C0 2 

Nitrogen monoxid, N 2 .... 


> . \ 


14 
22 
22 





CERTAIN CHEMICAL RELATIONS 



127 



2. It has been proven experimentally that one litre of 
hydrogen and one litre of chlorin form two litres of hydro- 
chloric acid ; hence, according to Avogadro's law, x molecules 
of hydrogen plus x molecules of chlorin form 2 x molecules 
of hydrochloric acid ; but in 2 & molecules of hydrochloric 
acid there are 2x atoms of hydrogen, therefore in each 
molecule of hydrogen there must be at least two atoms of 
hydrogen ; and further, the molecules of each of the first nine 
elements in the table must contain at least tivo atoms. 

Molecules which consist of tivo atoms are said to be diatomic. 

The following diagrams will assist the student in follow- 
ing this line of thought : — 



Molecules consist of Single Atoms 




<b <o<o 



Molecules consist of Two Atoms 





\6> 


% 9> 


1 


** 


si* 


? 




CO 

* 


MIXED 




% 


% 


f> 


•0 


*>> 


°# 


*>* 


*8 


OS 


d» 



• o • 2 o 
° • ° • o 

• • °. .° 


MIXED 





In the above diagrams an atom of hydrogen is represented 
by the symbol • , and one of chlorin by O. The size of 
the squares accords with the fact that one volume of hydro- 
gen and one volume of chlorin form two volumes of hydro- 
chloric acid. 



128 CHEMISTRY 

3. The atomic weights of sodium, potassium, zinc, and 
cadmium, are respectively twice their vapor densities. That 
is to say, whereas the atom of sodium is 23 times as heavy 
as the atom of hydrogen, a litre of sodium vapor is only 11.5 
times as heavy as a litre of hydrogen. Hence, in a litre 
of sodium vapor there are only half as many atoms as there 
are in a litre of hydrogen. But according to Avogadro's 
law, the number of molecules in the litre of sodium vapor 
is the same as the number of molecules in the litre of 
hydrogen; therefore, there are only half as many atoms in 
a molecule of sodium as there are in a molecule of hydrogen. 
If the hydrogen molecule is diatomic, the sodium molecule 
is monatomic, and so also are the molecules of potassium, 
zinc, and cadmium. Similar reasoning shows that the mole- 
cules of phosphorus and arsenic have twice as many atoms as 
the molecule of hydrogen. If hydrogen is diatomic, these 
elements are tetra-atomic, and the molecular weight is four 
times their atomic weight. 

4. It icill be observed that the density of any gas or vapor 
is numerically equal to half its molecidar iveight. This is due 
to the fact that molecular weights are expressed in terms 
of the weight of au atom of hydrogen, while the density is 
based upon the weight of a molecule of hydrogen. 

5. Inasmuch as there are equal numbers of molecules 
in equal volumes of all gaseous substances, we may learn 
from an equation expressing chemical action between gases 
the relative volumes of each of the factors and products, 
provided we are careful to write the reactions so that they 
express the relation between molecules instead of atoms. 
The equation 

H + CI = HC1 

is an atomic equation because two of the terms represent 
atoms, but if we write it thus, 



CERTAIN CHEMICAL RELATIONS 129 

H 2 + Clo = 2 HC1, 
it represents the action as taking place between molecules. 
From this equation we see that one molecule of hydrogen 
unites with one molecule of chlorin to form two molecules 
of hydrochloric acid; therefore, one volume of hydrogen 
unites with one volume of chlorin to form two volumes of 
hydrochloric acid. 

The equation K 2 + 3H 2 =2NH 3 

shows us that one volume of nitrogen unites with three 
volumes of hydrogen to form two volumes of ammonia. 
Every molecular equation which represents a reaction between 
gases expresses the volumetric relations of the factors and 
products. 

REVIEW QUESTIONS 

1. Give the symbols of a dibasic acid and the symbols of their 
salts which fully illustrate the basic properties of that acid. 

2. Name, define, and illustrate two great classes of salts. 

3. Write names and symbols of three univalent elements, three 
bivalent elements, and three trivalent elements. 

4. State the theory of valence. 

5. When are elements said to be in a nascent state ? What 
peculiarity do most substances exhibit when in this state ? Illustrate. 

6. What does the following equation teach us concerning the vol- 
umetric composition of water : — 

2 H 2 + 2 = 2 n 2 o. 

7. State the composition of sulfur dioxid by weight and by volume. 

8. State the valence of the metals forming chlorids having the fol- 
lowing formulas : CaCl 2 , KC1, NaCl. 

9. Sulfur forms a compound having the formula SH 2 . What is the 
valence of the sulfur ? 



CHAPTER XVII 

THE ALKALI METALS 

SECTION I.— POTASSIUM AND ITS COMPOUNDS 

182. Thus far we have considered only acid-forming 
elements. It is true that some of them manifest basic 
properties when combined with the stronger acid-forming 
elements, but considering all of their properties, they are 
classed with the acid-formers. We can have only time to 
discuss the most important basic elements, and a few of 
their compounds. The principal alkali metals are lithium, 
potassium, and sodium. Ammonium is treated as a member 
of this family because of its strong basic properties, but it 
must be remembered that it is a radical and not an element. 

POTASSIUM 
Symbol K. — Atomic Weight 39 

183. Occurrence. — Potassium is not found free in nature ; 
in combination, chiefly as a silicate it occurs in many min- 
erals. The older rocks, such as granite and gneiss, contain 
a large percentage of feldspar, a silicate of aluminum and 
potassium. Potassium compounds are necessary constitu- 
ents of all fruitful soils. ' They are absorbed by the plants, 
none of which can live without them. 

184. Preparation and Properties. — At one time the chief 
source of this element was wood ashes, from which it may 
be obtained as a carbonate. Xow the chief source is the 

130 



THE ALKALI METALS 131 

deposit of potassium salts found near Stassfurt in Germany. 
Metallic potassium is prepared by distilling the carbonate 
with charcoal, with the following reaction : — 

K 2 C0 3 +2C = 2K + 3CO. 

Potassium is a light metal with a bright metallic lustre, 
it floats on water, decomposing it with the evolution of 
sufficient heat to ignite the hydrogen liberated. The follow- 
ing equation explains the reaction which occurs : — 

K + H 2 = KOH + H. 

It oxidizes rapidly and must be kept under naphtha or 
some liquid which does not contain oxygen. Potassium 
and its compounds communicate a violet tint to flame. 

Experiment LXXIX. — Drop a small piece of potassium in water. 
Describe fully all that occurs. Xote the color of the flame. What 
gas has evolved ? What remained in solution ? Is it an acid or a 
base ? Test the water with litmus. 

185. Potassium Hydroxid, KOH (Caustic Potash). — This 
substance is prepared by heating potassium carbonate with 
slacked lime in an iron vessel. In what other way may it 
be prepared ? It is a white, brittle solid, usually cast into 
sticks, is extremely deliquescent, 1 and dissolves in water 
with evolution of heat. It is one of the strongest bases 
known, and is therefore an important reagent in the labo- 
ratory. It is also used in the manufacture of Bohemian 
glass and of soft soap. It attacks the flesh, and is some- 
times used as a cautery. 

186. Potassium Nitrate, KN0 3 (Saltpetre). — The occur- 
rence of this salt is discussed on pages 40 and 76. It 
is formed in warm climates by the action of microbes on 

1 Define term. 



132 CHEMISTRY 

organic refuse rich in nitrogen. Saltpetre plantations, 
where the salt is prepared artificially from soil in the 
neighborhood of ancient villages which has became satu- 
rated with animal refuse, are found in India, but the greater 
part of the potassium nitrate is now obtained by treating 
sodium nitrate with potassium chlorid. Potassium nitrate 
is a colorless crystal, very permanent in air, and easily solu- 
ble in water. It is an excellent oxidizing agent. Because 
of its permanence in air, it is extensively used in the manu- 
facture of gunpowder and in pyrotechny. 

187. Gunpowder is a mixture of saltpetre, charcoal, and 
sulfur, the proportion varying somewhat in the different 
grades, but it is approximately as follows : — 

Saltpetre 75% 

Charcoal 15 % 

Sulfur 10% 

Its explosive power is due to a complex chemical change 
which converts about half of its weight into gases; the 
remainder of the powder forms solids which cause the 
"smoke," and which render frequent cleaning of the gun 
necessary. The explosion of ordinary gunpowder forms 
seven different gases and ten solids. The smokeless 
powders are converted into gases only. 

188. Potassium Chlorate, KC10 3 , is chiefly valuable as an 
oxidizing agent. It is used in making parlor matches, in 
fireworks, medicine, and dyeing. 

Experiment LXXX. — Place a little potassium chlorate in a beaker, 
cover it with water, drop a small piece of phosphorus into the water. 
and pour about \ cc. of concentrated sulfuric acid through a funnel 
tube which extends to the bottom of the beaker. Does combustion 



THE ALKALI METALS 133 

take place ? What substances present might furnish oxygen for com- 
bustion ? Did it occur before the sulfuric acid was added ? Does 
it occur if potassium chlorate is absent ? Try it. Whence does the 
oxygen come ? State the physical properties of potassium chlorate. 

189. Potassium Carbonate, K 2 C0 3 . — In America this salt 
is usually prepared by leaching wood ashes. The ashes are 
placed in a barrel, water is poured on them and drawn off 
at the bottom. It dissolves the soluble salts. The potash 
lye thus obtained contains considerable quantities of potas- 
sium carbonate. The salt is prepared from the liquid by 
evaporation, and is known as potash. When refined it is 
called pearl-ash. It is a deliquescent salt with a strong 
alkaline reaction. 

190. Potassium Acid Carbonate, KHC0 3 (Saleratus). — This 
familiar salt is prepared by passing a current of carbon 
dioxid through a solution of the normal carbonate. 

Uses. — Cooking, bleaching hair. 

SECTION II. — SODIUM 
Symbol Na. — Atomic Weight 23 

191. Occurrence. — The compounds of sodium are widely 
distributed, and some of them are found in enormous de- 
posits. The chlorid is the most abundant, but large deposits 
of the nitrate, carbonate, silicate, and borate are found in 
certain parts of the world. 

192. Preparation and Properties. — Sodium is prepared by 
distilling sodium carbonate with charcoal. It resembles 
potassium in its physical and chemical properties. It 
floats on water, decomposing it, but does not always ignite 
the evolved hydrogen. Ifc oxidizes rapidly in the presence 
of moisture, and is used as a reducing agent in the prep- 



134 CHEMISTRY 

aration of certain metals. "When sodium and potassium 
are melted together under petroleum, an alloy is formed 
which is a liquid at ordinary temperatures, and which is 
used in themometers for measuring high temperatures 
which would vaporize mercury. Sodium and all of its 
compounds impart a yellow color to flame. 

193. Sodium Hydroxid, NaOH (Caustic Soda), like potas- 
sium hydroxid, is prepared by boiling a solution of sodium 
carbonate with calcium hydroxid. It resembles potassium 
hydroxid in appearance and in chemical properties, but 
does not deliquesce as rapidly. It is used in the manu- 
facture of glass and soap and in many chemical processes. 

194. Sodium Chlorid, NaCl, was formerly obtained by 
evaporating sea-water, but the discovery of large natural 
deposits of "rock salt" has diminished its value so as to 
render this process unprofitable in most countries. At 
Piffard and at Warsaw, N.Y., salt is taken from the mine 
in solid form. If the salt is mixed with earthy impurities, 
water is allowed to flow into the mines, and after a time is 
pumped out and evaporated. Sodium chlorid crystallizes in 
transparent cubes; it is necessary to animal life. In the 
arts, it is extensively used in the alkali industry, in the 
process of glazing earthenware, in reducing silver, and in 
preserving meats and fish. 

195. Sodium Carbonate, Na 2 C0 3 . — This salt is the alkali 
of the arts, and is almost as extensively used as sulfuric 
acid ; in the manufacture of glass and soap large quantities 
are annually consumed. It occurs in nature in some of the 
western states, and also in Hungary and in Africa. Trior 
to 1808 sodium carbonate was obtained from the ashes of 
sea-plants, which extract it from the salt water just as land 



THE ALKALI METALS 



135 



plants absorb potassium from the soil ; but during the 
French Kevolution, the government being unable to obtain 
it, offered a large reward for a process of making it from 
common salt. Leblanc won the prize, and the process 
which bears his name has been extensively used ever since. 
In the Leblanc process sodium chlorid is first heated with 
sulfuric acid in a covered cast iron pan, D (figure 16). The 
hydrochloric acid formed is conducted to the condensing 




towers through the pipe E; when the mass begins to 
solidify, the slide h is raised and the mass raked out onto 
the hearth B of a reverberatory furnace. Here it is heated 
to dull redness by a coke fire at A. This converts the salt 
into the normal sodium sulfate, — 

2 NaCl + H 2 S0 4 = 2 HC1 + Na 2 S0 4 . 

The acid evolved during this process is also conducted to 
the condensing towers through the pipe F. The " salt cake " 
taken from the hearth is mixed with limestone (calcium 
carbonate) and coal dust, and again heated to a high tern- 



136 CHEMISTRY 

perature on the hearth of a furnace, when the following 
reaction occurs : — 

Na 2 S0 4 + CaC0 3 + 2 C = Na 2 C0 3 -f CaS + 2 CO* 

The black ash formed in this furnace contains something 
less than half its weight of sodium carbonate. The other 
substances found in the black ash are insoluble in water; 
the sodium carbonate is therefore dissolved out. The solu- 
tion is evaporated and the residue calcined at a red heat. 
This forms a nearly pure, anhydrous sodium carbonate 
known in commerce as soda-ash. If it is redissolved and 
allowed to crystallize, the common washing soda is obtained, 
having the composition Na 2 C0 3 , 10 H 2 0. 

In the Solvay process, which is much cheaper than the 
Leblanc, ammonia is passed through tanks containing brine. 
This precipitates magnesia and calcium carbonate, and 
raises the temperature of the liquid, which is decanted, 
filtered, and cooled, and then passed through the carbonat- 
ing tower. The tower is about 50 feet high and 6 feet in 
diameter. At intervals of about 3 feet there are compound 
diaphragms consisting of a horizontal plate with a large 
hole in the centre, and over this a curved plate perforated 
with small holes and deeply notched around the edge. The 
brine is introduced near the top, and carbon dioxid is forced 
into the brine near the bottom of the tower and passes 
upward through the holes in the diaphragms. In this 
tower the principal reaction occurs : — 

NaCl + NH 3 + C0 2 + H 2 = NaHC0 3 + NH 4 C1. 

The hydrogen sodium carbonate thus formed is less 
soluble than the ammonium chlorid; it therefore crystal- 
lizes first as the solution approaches saturation, and collects 
at the bottom of the tower. The ammonium chlorid funned 



THE ALKALI METALS 137 

is treated with calcium hydrate, and the ammonia liberated 
is used to saturate more of the brine. A lime-kiln is 
usually maintained in connection with Solvay plants, to 
furnish the lime used in recovering the ammonia, and most 
of the carbon dioxid required is obtained from the waste 
gases of the kiln. It thus appears that the raw materials 
required for the Solvay process are common salt, limestone, 
and a supply of ammonia which is used over and over 
again. The materials required for the Leblanc process are 
common salt, sulfuric acid, limestone, and coal, neither of 
which is used again. 

Notwithstanding the fact that hydrogen sodium car- 
bonate is the only product as yet obtained from the Solvay 
process, whereas the Leblanc process yields hydrochloric 
acid and sulfur in addition to sodium carbonate, the greater 
cost of the raw material, together with the inferior quality 
of the Leblanc product, places the Leblanc process at such 
a disadvantage that at the present time the Solvay process 
supplies considerably more than half of the soda-ash of 
commerce. The hydrogen sodium carbonate is converted 
into normal carbonate by calcination. 

196. Hydrogen Sodium Carbonate, HNaC0 3 (Sodium Bicar- 
bonate or Baking Soda). — This substance maybe prepared 
by passing carbon dioxid through large cylindrical towers 
filled with the normal carbonate, but the greater part of the 
hydrogen sodium carbonate of commerce is prepared by 
the Solvay process, described in the preceding article. 
Its crystals contain no water of crystallization; they dis- 
solve readily in eleven parts of water, the solution having 
a feeble alkaline reaction. Boiling a solution of this salt 
disengages carbon dioxid, converting the salt into the nor- 
mal carbonate. It is a valuable reagent in the laboratory, 



138 CHEMISTRY 

is the principal alkali used by cooks, and is used in medi- 
cine to a limited extent. 

197. Baking Powders are mixtures which evolve gas when 
moistened, and are chiefly used as substitutes for yeast. A 
common form is prepared by mixing cream of tartar, 
KH 5 C 4 6 , 56 % ; hydrogen sodium carbonate, 25 % ; and 
starch, 19 %. Tartaric acid is sometimes used instead of 
cream of tartar, but these powders do not keep as well as 
the above. When this mixture is moistened, carbon dioxid 
is evolved as it is during fermentation, and the purgative 
Rochelle salts remain in solution. When cake or biscuits 
are raised with baking powder the escaping carbon dioxid 
renders the dough light. Professor Horsford has patented 
a baking powder consisting of dried phosphoric acid and 
hydrogen sodium carbonate. Carbon dioxid is evolved, and 
sodium phosphate remains in the dough. The best baking 
powder of the ordinary class is one containing only cream 
of tartar and hydrogen sodium carbonate, but these powders 
do not retain their leavening power very long unless starch 
or some equivalent is added. Many of the commercial 
articles contain either alum or ammonium carbonate, and 
some of them contain both. 

SECTION III.— AMMONIUM SALTS 

198. The compounds of the radical NH4 are treated here 
because they resemble those of sodium and potassium. In 
its chemical affinities ammonium behaves like a basic element. 

199. Ammonium Chlorid, NH,C1, is prepared by neutraliz- 
ing the ammoniacal liquor of the gas works with hydro- 
chloric acid and evaporating the solution to dryness, the 
residue is heated in iron vessels, when ammonium chlorid 
sublimes. 



THE ALKALI METALS 139 

It has a sharp, saline taste, is soluble in water, and, when 
heated in contact with a metal, it either dissolves the coat- 
ing of oxid (rust) on the metal or converts it (the rust) into 
a chlorid, thus leaving a bright surface. 

Because of this property it is extensively used in solder- 
ing and in galvanizing and tinning metals. When heated 
it sublimes, that is to say, it passes from a solid state 
into a vapor without perceptible liquefaction. Ammonium 
chlorid is commonly called sal ammoniac. It is largely 
used as the exciting liquid in batteries and is also employed 
in calico printing and in medicine. 

200. Ammonium Nitrate is prepared by neutralizing nitric 
acid with ammonia and evaporating the solution until it 
crystallizes on cooling. 

When heated rapidly, as by contact with a red-hot metal, 
it detonates, as it does also when heated in contact with 
organic matter. It dissolves readily in water, producing a 
marked drop in temperature. 

Uses. — Preparing nitrogen monoxid, in certain explosives, 
also in freezing mixtures. 

201. Ammonium Carbonate. — The commercial article (sal 
volatile or " smelling salts ") is a somewhat unstable mix- 
ture of hydrogen ammonium carbonate and ammonium car- 
bonate which smells strongly of ammonia. The normal 
carbonate, (]STH 4 ) 2 C0 3 , and the acid carbonate, £N"H 4 )HC0 3 , 
are easily obtained. 

Uses. — In medicine, in the laboratory, and by bakers. 
It is the cause of the odor of ammonia frequently detected 
in bakers' cake. 

202. Ammonium Sulfid, (NH 4 ) 2 S. — The principal use of 
this substance depends upon the ease with which it is de- 



140 ^CHEMISTRY 

composed by the compounds of certain bases. These bases 
are precipitated as sulfids, and thus may be easily separated 
from other elements in the process of qualitative analysis. 
The solution of ammonium sulfid forms a colorless liquid 
of disagreeable odor, which gradually turns yellow because 
of the formation of compounds known as poly-sulfids of 
ammonia, having the formulas (XH 4 ) 2 S 2 ; (NH 4 ) 2 S 3 ; etc. 

203. Ammonium Hydrosulfid, NH 4 HS. — This substance 
corresponds to the acid salts in having only one of the 
hydrogen atoms of hydrogen sulfid replaced. 

The compounds of the alkali metals, including am- 
monium, are isomorphous. Their chemical properties are 
related to their atomic weights. 

REVIEW QUESTIONS 

1. What is baking powder ? What is the theory of its action ? 

2. What is gunpowder ? Describe its manufacture. 

3. State a method of preparation of an aqueous solution of potas- 
sium hydroxid from metallic potassium. 

4. Give the names, formulas, and uses of three important com- 
pounds of sodium. Describe some process of making sodium car- 
bonate. 

5. State the composition of black gunpowder and explain the 
function of each of the chemicals. 

6. Discuss the physical and chemical properties of potassium. 

7. How is ammonium nitrate prepared ? What substances are 
formed when it is decomposed by heat? 

8. Define isomorphous. (Consult dictionary. ) 

9. For what purpose have you used ammonium nitrate ? What 
occurs when it is heated ? 



CHAPTER XVIII 
CALCIUM 

Symbol Ca. — Atomic Weight 40 

204. Occurrence. — In combination with, other elements, 
calcium occurs in enormous quantities. Limestone, marble, 
and chalk are calcium carbonate, CaC0 3 . Gypsum is calcium 
sulfate, CaS0 4 ; fluorspar is calcium fluorid, CaF 2 . A natural 
phosphate, Ca 3 (P0 4 ) 2 , occurs in large quantities in Florida. 

205. Preparation and Properties. — Calcium is prepared by 
electrolizing fused calcium chlorid. It is a yellowish metal, 
many times more valuable than gold. Like potassium 
and sodium, it decomposes water and cannot be kept in 
moist air; it is seen only in collections of elements. 

206. Calcium Oxid, CaO (Quicklime). Preparation. — Lime- 
stone is heated in a large furnace or kiln, carbon dioxid 
is driven off, and calcium oxid or quicklime remains in the 
furnace. CaC0 3 = CaO + C0 2 . 

Properties. — Lime is an amorphous, white, infusible solid. 
It has a strong affinity for water, combining with it to form 
the hydroxid or water-slaked lime with the evolution of much, 
heat. Exposed to the air, it slowly absorbs moisture and 
carbon dioxid, and falls to a powder known as air-slaked 
lime, one of the forms of CaC0 3 . When heated in the 
oxy hydrogen flame it gives forth an intense light of about 
120 candle power, which is known as the calcium light. 
141 



142 CHEMISTRY 

Uses. — In making mortar and cement, in the calcium 
light, and for drying gases in the manufacture of illumi- 
nating gas, as well as in the laboratory. 

207. Calcium Hydroxid, Ca(0H) 2 . Preparation. — As stated 
above, by treating calcium oxid with about one-third of its 
weight of water. 

Properties. — It is a white, alkaline, caustic powder, some- 
what soluble in water, and having a strong affinity for car- 
bon dioxid and hydrogen sulfid. It attacks animal tissues, 
as is shown by a plasterer's hand, and by its use in remov- 
ing hair from hides in the tannery. 

Uses. — Making mortar and whitewash, purifying gas, 
and in making brown sugar and glucose. Lime water is a 
solution of calcium hydroxid in water. 

208. Calcium Carbonate, CaC0 3 . Occurrence. — Calcite, 
chalk, marl, marble, Mexican onyx, and limestone are 
nearly pure calcium carbonate. It is the chief constituent 
of the shells of mollusks, corals, etc. 

Properties. — It is sparingly soluble in water, but dis- 
solves readily in water containing carbon dioxid, from 
which it is precipitated when the water loses its carbon 
dioxid. The formation of stalactites, stalagmites, travertin, 
etc., illustrate this property. 

Uses. — Making quicklime, building, making glass, reduc- 
ing iron ore, etc. 

209. Calcium Chlorid, CaCl,. — The properties of this sub- 
stance are very different from those of the so-called " chlorid 
of lime." This salt is odorless, it deliquesces,* it has a 
strong affinity for water, and absorbs it from air or moist 

* Define term. 



CALCIUM 143 

210. Calcium Chloro-hypochlorite, Ca(0Cl)Cl. — This com- 
pound is extensively used in the arts under the name of 
bleaching powder, and is often wrongly called " chlorid of 
lime." It is prepared by treating slaked lime with chlorin. 
It is a white powder with an odor resembling hypochlorous 
acid. When treated with a strong acid it gives np all its 
chlorin. When treated with carbon dioxid it gives up 
hypochlorous acid. Exposed to the air, the carbon dioxid 
liberates the acid slowly, hence its action as a disinfectant. 

211. Calcium Sulfate, CaS0 4 , is found in nature as the min- 
eral anhydrite, and in a hydrated condition as satin spar, 
alabaster, and selenite, which are different varieties of gyp- 
sum, CaS0 4 -f 2 H 2 0. When slightly heated it loses its water 
of crystallization, and falls to a powder known as plaster of 
paris (CaS0 4 ) 2 H 2 0. This substance has a strong affinity for 
water, and when treated with it takes up the water of crys- 
tallization previously expelled, and hardens or " sets." 

(CaS0 4 ) 2 H 2 + 3 H 2 = 2(CaS0 4 + 2 H 2 0). 
Uses. — Gypsum is extensively used as a substitute for 
marble in buildings, as a fertilizer, and in the manufacture 
of plaster of paris. Plaster of paris is used as a cement ; 
e.g. in incandescent lamps and in making casts. 

212. Glass. — Ordinary window glass and bottle glass are 
silicates of calcium and sodium. In the manufacture of 
bottle glass somewhat impure materials may be used, and 
its green color is due to the presence of small quantities of 
the silicates of aluminum and iron. In window glass, as 
this green color is an objection, the purest materials obtain- 
able are used. The color due to the small amount of iron 
which they contain is partially corrected by adding a small 
quantity of manganese dioxid. Bohemian glass, a silicate 
of potassium and calcium, has a higher melting point than 



14-4 CHEMISTRY 

window glass, and on this account is largely used for chemi- 
cal apparatus. Flint glass contains lead instead of calcium ; 
it fuses easily, and is extensively used for optical instruments. 

Glass Making. — At the Kochester glass works the follow- 
ing substances are melted for bottle glass : Clean sand, 
100 lbs. ; soda-ash, 40 lbs. ; lime, 28 lbs. ; feldspar, 1 lb. 
It requires from 12 to 14 hours to complete the melting. 

Colored glass is made by adding a small quantity of a 
metallic oxicl. Thus, cobalt colors glass blue ; chromium, 
green ; iron, green ; gold, red ; amber glass is made by add- 
ing soft coal. 

Suggestion. — Write an essay on processes of melting, blowing, 
and annealing glass, making window glass, plate glass. 

213. Mortar is made by mixing one part of lime with 
water to a thin paste, then adding three or four parts of 
coarse, sharp sand, and thoroughly incorporating these 
ingredients. When mortar is exposed to the air, calcium 
carbonate is slowly formed. Water is formed as the calcium 
hydroxid is transformed into the calcium carbonate. 

CaH 2 2 + C0 2 = CaC0 3 + H 2 0. 
This explains why plaster dries so slowly. The complete 
conversion of lime into carbonate requires a very long time, 
because the carbonate which is formed at first protects the 
rest. Booms heated by open coke and charcoal fire dry 
more rapidly because the carbon dioxid which escapes into 
the room provides an abundant supply for the above reaction. 

REVIEW QUESTIONS 

1. Why does mortar harden ? 

2. Why is hair used in plaster ? 

3. Why not in bricklaying ? 

4. Why does plaster of paris set when treated with water ? 

5. What is mortar ? What chemical action occurs when it hardens ? 



CALCIUM 145 

6. What is glass ? How is it made ? 

7. How does Bohemian glass differ from window glass ? 

8. What will dissolve glass ? 

9. Describe the preparation of quicklime, writing the reaction. 

10. Mention two important uses of calcium oxid. 

11. Describe a lime-kiln. 

12. Give the chemical names of plaster of Paris, marble, gypsum, 
and quicklime. 

13. State the common names of calcium hydroxid and calcium 
chloro-hypochlorite. 



CHAPTER XIX 

SILVER, COPPER, AND GOLD 

SILVER 

Symbol Ag. — Atomic Weight 108 

214. Occurrence. — Silver occurs uncombined in nature, 
but its most important ores are the sulfids and chlorids. 
Silver sulfid may be nearly always detected in the sulfids 
of other metals. 

215. Properties. — Silver is a white metal permanent in 
air at ordinary temperature. Hydrogen sulfid acts readily 
upon it, forming a black coating of silver sulfid. It is the 
best conductor of heat and electricity known. 

216. Extraction from its Ores, (a) Pattinson process. — 
Silver is extracted from ores consisting of mixed sulfids of 
lead, silver, etc., by the Pattinson process. The ore is 
roasted until the sulfur is expelled, and an alloy of silver 
and lead remains. This alloy is melted in large kettles and 
allowed to cool ; the lead solidifies first and is dipped out. 
By this means a product is finally obtained which contains 
a high percentage of silver. This is heated in a stream of 
air, the lead oxidizes, and the silver remains ; when all the 
lead has been removed, the silver reflects light, and the 
operator sees his face in the molten metal. This depends 
upon the fact that lead solidifies at higher temperature 

146 



SILVER, COPPER, AND GOLD 147 

than an alloy of lead and silver, and also upon the fact 
that lead oxidizes while silver is permanent. 

(b) Amalgamation process. — Other ores of silver are 
reduced by the amalgamation process. The ore is thor- 
oughly ground, mixed with common salt, and roasted, thus 
transforming all of the silver into a chlorid. The roasted 
mass is then placed in suitable vessels with water, iron 
scraps, and mercury, and vigorously agitated for many 
hours. The iron decomposes the chlorid, and the silver 
thus liberated forms an amalgam with the mercury. A 
portion of the mercury is removed by pressure, and the 
remainder by distillation, leaving the pure silver in the 
retort. The mercury is collected and used again. 

217. Uses. — In jewellery, coins, etc., and in protecting 
other metals from the action of the air by electroplating. 

218. Silver Nitrate, AgN0 3 . — In contact with organic 
matter it turns black when exposed to the sunlight, hence 
it is a constituent of indelible inks. It corrodes the flesh, 
and is used by physicians to burn out wounds. It is some- 
times called lunar caustic. 

219. Photography. — The most important property of the 
salts of silver is their changing when exposed to light. The 
chlorids, bromids, and iodids are extensively used in pho- 
tography. "A plate of glass is coated with the salt of 
silver, the plate is then exposed in a camera to light coming 
from the object to be photographed." The salt is changed 
where light strikes it, the amount of the change being 
proportionate to the intensity of the light. The image does 
not appear on the plate until after it is treated with a reduc- 
ing agent, usually pyrogallic acid. After the image is 



148 CHEMISTRY 

developed, the unchanged silver salt is dissolved off with 
sodium hypos ulfite. 

COPPER, Cc, 63.6 

220. Occurrence. — Copper occurs native in large quanti- 
ties near Lake Superior, in Chili, etc. In combination it is 
found as ruby copper, Cu 2 0, as copper pyrites, a sulfid of 
iron and copper, and as a carbonate. 

221. Preparation and Properties. — The oxid of copper is 
reduced by heating with charcoal. It is a hard reddish 
metal, having a metallic lustre. In moist air it becomes 
coated with a layer of carbonated copper. Copper forms 
two distinct series of compounds. There are two chlorids : 
cuprous chlorid, Cu 2 Cl 2 , and cupric chlorid, CuCl 2 : also two 
sulfates, two oxides, etc. Copper sulfate, CuS0 4 + 5 H 2 
(common name, blue vitriol), is largely used in galvanic 
batteries and in calico printing. 

GOLD 
Symbol Au. — Atomic Weight 197 

222. Occurrence and Reduction. — This element is seldom 
found in combination in nature. In the parent ledges it 
occurs as isolated particles surrounded by quartz. As the 
ledge weathers, the particles of gold are carried down the 
streams with the quartz sand, forming placer deposits like 
those of the Klondike. At the ledge the rock is pulverized 
and carried over amalgamated copper plates by a stream of 
water. The gold forms an amalgam with the mercury, 
which is carefully removed and distilled. The gold of the 
placer deposits is recovered by mechanical washing. 

223. Properties. — Gold is a soft, yellow metal, not 
affected by air or oxygen, even at high temperatures. It 



SILVER, COPPER, AND GOLD 149 

is very malleable, easily beaten into sheets .0001 of a milli- 
metre thick. When examined by transmitted light, these 
sheets appear green. It is very easily reduced ; most metals 
precipitate it from solution, hence its use in toning photo- 
graphs. 

224. Uses. — Pure gold is too soft for use. Advantage 
is therefore taken of the fact that it forms alloys with 
copper and silver, either of which is more durable than 
pure gold. In Germany, France, and the United States 
the standard gold coin contains 90 % of gold and 10 % of 
copper. English gold pieces contain 11 parts of gold to 
1 of copper. The metal with which gold is alloyed is 
easily recognized by the color of the alloy ; that of copper 
having a reddish color, while that of silver is paler than 
pure gold. The fineness of gold jewellery is still expressed 
in carats. The carat is an old weight equal to the weight 
of four barleycorns, or -^ of a Troy ounce. Jewellery is 
said to be 18 carats fine when a Troy ounce contains 18 
carats of pure gold. 

REVIEW QUESTIONS 

1. Describe the process of extracting silver from its ores by amal- 
gamation, giving chemical changes that take place. 

2. Describe the process of photography, explaining the use of the 
compounds of silver employed. 

3. State the common name, properties, and uses of silver nitrate. 

4. Erom what acid was silver nitrate obtained ? 

5. State the properties of silver chlorid. 

6. How does copper occur in nature ? Eor what purposes is it 
used ? Describe its most important compounds. 

7. Discuss the occurrence of gold in nature. 

8. Describe the extraction of gold from its ores, and state its prin- 
cipal uses. 

9. Explain the blackening of silver spoons when in contact with 
boiled eggs. 



CHAPTER XX 

ZINC AND MERCURY 

ZINC 
Symbol Zn. — Atomic Weight 65.4 

225. Occurrence. — Zinc is said to have been found in 
Australia in the uncornbined condition. In combination it 
is found as a carbonate, ZnC0 3 (calaniin), as a sulfid, ZnS 
(zinc blende), as the red oxid, ZnO, and as a silicate. 

226. Preparation. — The ores are first calcined, to reduce 
them to an oxid, and then mixed with charcoal and raised 
to a high temperature. The zinc oxid is reduced and the 
metal vaporized and condensed in iron vessels. 

227. Properties. — Zinc is a bluish white metal, with a 
crystalline fracture; it melts at 412° C. and vaporizes at 
about 1000° C. It is exceedingly brittle, except between 
100° and 150° C, when it is malleable, and may be rolled 
out into sheets. It is very soluble in acids, and burns in 
air with an intense blue light, forming zinc oxid, ZnO, a 
white flocculent substance formerly known as philosophers' 
wool. Zinc is permanent in air, because the coating of zinc 
oxid which forms when first exposed to the air prevents 
further oxidation. 

228. Uses. — Zinc is extensively used in batteries and as 
a coating for other metals to protect them from the action 

150 



ZINC AND MERCURY 151 

of the air. Galvanized iron is sheet iron coated with zinc, 
not by electricity, as the name would indicate, but by dip- 
ping the iron in molten zinc. Several important alloys 
contain zinc ; e.g. brass, German silver, and the bronze used 
for coinage. 

229. Principal Compounds. — Zinc oxid, ZnO, is a pure 
white substance, although it occurs native as the red zinc 
ore, its color being due to small amounts of manganese. It 
is often used as a substitute for white lead, because it is 
not blackened by hydrogen sulfid found in the air. Zinc 
chlorid, ZnCl 2 , is a soft solid which may be distilled with- 
out decomposition. It has a strong affinity for water, ab- 
sorbing it from the air, hence its use as a drier of gases. 
It is an excellent deodorizer, and is an important constitu- 
ent of some of our best disinfectants. It is quite generally 
used by tinsmiths as a soldering fluid, as its aqueous solu- 
tion dissolves the oxids which might prevent the adherence 
of the solder. It is also used to prevent timber from decay 
and to a limited extent as a caustic in surgery. When zinc 
oxid is moistened with zinc chlorid, a paste is formed which 
hardens quickly and is used in dentistry. 

MERCURY 
Symbol Hg. — Atomic Weight 200 

230. Occurrence and Preparation. — Mercury occurs free 
in nature, but the principal source from which it is obtained 
is cinnabar, a natural sulfid, which is found in California, 
Mexico, Peru, Spain, China, etc. Cinnabar is roasted and 
the vapor of mercury condensed in su,. cable vessels. 

231. Properties. — Mercury is the only liquid metal. It 
has a silver-white color, hence its former name, quicksilver ; 



152 CHEMISTRY 

it freezes at — 39.5° C. ; it volatilizes, and the vapor is 100 
times as heavy as hydrogen. From this fact it appears 
that mercury is mon atomic when a vapor. Mercury forms 
a soft alloy with most metals except iron. The alloys of 
mercury are called amalgams. 

232. Uses. — Mercury is used in thermometers, barome- 
ters, pressure gauges, and other instruments. Chemists use 
it in collecting gases, and dentists use an amalgam of 
mercury and cadmium as a filling for teeth. In the arts 
it is extensively used in making mirrors and in the pro- 
cesses of extracting gold and silver from their ores. It 
is also used in voltaic cells. 

233. Compounds — Mercury forms two series of salts, the 
mercurous, like calomel, Hg 2 Cl 2 , and the nitrate, Hg 2 (N0 3 ) 2 , 
in which the double atom is bivalent; and the mercuric 
salts, like corrosive sublimate, HgCl 2 , and the mercuric 
nitrate, Hg(X0 3 ) 2 , in which the atom is bivalent. 

REVIEW QUESTIONS 

1. For what purpose is zinc chlorid used ? 

2. What is galvanized iron ? Why is iron galvanized ? 

3. State the properties of zinc. 

4. What important alloys contain zinc ? 

5. What are the chief ores of zinc ? 

6. Describe the physical properties of mercury. 

7. Why is mercury used for thermometers ? Barometers ? What 
are the freezing and boiling points of mercury ? 

8. Describe the action of heat on mercuric oxid. 

9. Mention some metals that will amalgamate with mercury. 

10. What is cinnabar ? How would you prove that it contains 
mercury ? 



CHAPTER XXI 
ALUMINUM 

Symbol Al. — Atomic Weight 27 

234. Occurrence. — Aluminum is one of the most abun- 
dant elements. It is never found unconibined, but occurs 
in combination in most rocks and therefore in nearly all 
soil. Among the many common minerals which contain it 
are feldspar, mica, cryolite, corundum, and bauxite. Emery 
is an impure corundum. Several valuable gems contain 
aluminum. The ruby, sapphire, and oriental topaz are 
transparent crystals of corundum, A1 2 3 , the difference 
between them being due to the presence of small quantities 
of certain oxids. True topaz is a silicate of aluminum. 
The emerald is a double silicate of aluminum and berylium. 

235. Reduction. — Until the invention of the electric fur- 
nace metallic aluminum was very expensive because metallic 
sodium was used in reducing it. Formerly it was worth 
$ 20 a pound, but now the price is about 40 cents. Most of 
the metal is now obtained from bauxite, A1 2 3 , H 2 0, or from 
corundum, A1 2 3 . A wrought iron furnace is lined with 
carbon and partly filled with an artificial cryolite. Large 
carbon rods are thrust into the mass, and a powerful cur- 
rent sent from the rods through the mass to the furnace; 
the cryolite is melted, and dissolves the ore which is thrown 
in from time to time. The oxid is electrolyzed by the cur- 
rent, and metallic aluminum collects at the bottom of the 
furnace, while oxygen appears at the anode. 

153 



154 CHEMISTRY 

236. Properties. — Aluminum is a white lustrous metal, 
its color is between that of silver and that of zinc. It is 
very light (Sp. gr. 2.56, which is about one-quarter that of 
silver and about the same as that of glass). It is very 
malleable, is easily cast, is tenacious, and is more rigid than 
equal weights of other metals. It cannot be welded except 
by electricity. It is permanent in moist as well as dry air, 
even at moderately high temperatures. It melts at about 
650° C, and is an excellent conductor of both heat and 
electricity. It is dissolved by hydrochloric acid and by 
solutions of sodium and potassium hydrates, but is not 
soluble in either sulfuric or nitric acids. 

237. Uses. — The use of aluminum has rapidly increased 
within a year or so, and is now employed for many articles, 
from hairpins to horseshoes ; from stove hollow ware to 
flying machines. Aluminum forms valuable alloys with 
copper and with steel ; the most important of these is the 
aluminum bronze, which contains 90 % of copper and 10 % 
of aluminum. It has the color of gold, the tenacity of 
steel, takes a high polish, and does not tarnish in air. 

238. Compounds. — Aluminum sulfate forms compounds 
with either sodium or potassium or ammonium sulfates, 
which belong to a class of double sulfates known as alums. 
All of the alums form beautiful cubical or octohedral 
crystals. Twenty-five different kinds are known, but only 
potassium alum, KA1(S0 4 ) 2 + 12 H 2 0, and ammonium alum, 
NH 4 A1(S0 4 ) 2 + 12 H 2 0, are common. Alum is extensively 
used as a mordant by calico printers and dyers ; it increases 
the amount of coloring matter which cotton cloth can 
absorb, and makes the color more permanent. Alum is 
often wrongly used as a constituent of cheap baking 
powder. 



ALUMINUM 155 

239. Hydraulic Cement, which, is made by burning a lime- 
stone that contains aluminum silicate, owes its ability to 
set or harden when mixed with water to the formation of 
silicates of calcium and aluminum. As these silicates are 
insoluble in water, the cement may be used for submerged 
masonry. 

240. Ordinary clay is an impure aluminum silicate ; when 
mixed with water it forms a plastic mass which may be 
easily moulded into any desired shape, and which becomes 
hard, brittle, and very durable when dried and baked in a 
suitable furnace. The common clays are used in the manu- 
facture of brick tile and earthenware. 

Earthenware and tile are rendered impervious to water, 
or glazed, by throwing common salt into the furnace just 
before the "firing" is finished; the salt volatilizes, and 
forms a coating of sodium and aluminum silicate on the 
surface of the earthenware. The color of bricks and 
earthenware is largely due to the presence of iron oxids in 
the clay. 

241. Porcelain clay or kaolin is a very pure silicate, 
Al 4 (Si0 4 ) 3 H 2 0. In making porcelain a fine mixture of 
kaolin, feldspar, and quartz is employed. On strong igni- 
tion feldspar fuses, fills the pores of the clay, and thus fur- 
nishes a fused transparent mass. The finest porcelain is 
dried and heated to a red heat, forming a porous ware 
known as biscuit. This is dipped in water in which a 
small quantity of finely powdered feldspar is suspended. 
The article is now raised to a white heat, the feldspar 
increases the, fusibility of the surface, and a thin, smooth, 
glassy coating results. The colors used in decorating are 
usually metallic oxids, and are almost always applied over 
the glaze in the better work. 



156 CHEMISTRY 



REVIEW QUESTIONS 



1. Discuss the physical and chemical properties of aluminum. 
Describe a process by which it may be extracted from some ore. 

2. What is clay ? How was it formed ? 

3. What is the chemical composition of alum ? 

4. Describe the metal aluminum. What name is given to its 
oxid? 

5. What is hydraulic cement ? 

6. How does porcelain clay differ from the ordinary article ? 

7. State the occurrence in nature and uses of aluminum. 

8. Mention the principal compounds of aluminum which occur in 
nature. 

9. What is porcelain ? How is it glazed ? 

10. State the uses of alum. 

11. What advantage does aluminum possess over iron ? 

12. What alloys contain aluminum ? 



CHAPTER XXII 
IRON 

Symbol Fe. — Atomic Weight 56 

242. Occurrence. — Iron is one of the most abundant as 
well as one of the most useful metals ; it occurs uncombined 
in meteorites and in minute particles distributed through 
certain crystalline rocks. In combination with oxygen it 
occurs in enormous quantities in the older rocks, as magni- 
tite, Fe 3 4 , which contains more than 72 % of iron ; hematite, 
Fe 2 3 , with TO % of iron ; and as limonite, 2 Fe 2 3 + 3 H 2 0, 
a hydroxid with about 60 % of iron. 

Siderite, FeC0 3 , is an important ore. Iron occurs as a 
sulfid known as pyrite, which is used in the manufacture of 
sulfuric acid, but which is not yet used as an ore. Most 
of the iron in this country is obtained from the oxids, but 
in England the principal source is "clay ironstone," a 
carbonate mixed with clay. 

243. Extraction from its Ores. — If the ore is a carbonate 
or a hydroxid, it is calcined to expel the carbon dioxid or 
the water, and thus convert it into an oxid. The oxid is 
reduced by heating with carbon, usually a specially prepared 
coke made from soft coal. Charcoal is used in Sweden and 
Norway, where wood is plentiful. Most ores contain more 
or less silica and alumina, which must be converted into 
fusible silicates ; to effect this, limestone is added to the 
mixture of ore and carbon, and a double silicate of calcium 

157 



158 



CHEMISTRY 



and aluminum, a crude glass called slag, is formed. These 
reactions are brought about in a blast furnace (Fig. 17). 
It consists of a masonry tower some 80 feet in height and 
from 15 to 25 feet in diameter, lined with a most infusible 
fire-brick. Coke, limestone, and iron ore are introduced at 

the top in alternate 
layers by means of a 
cup and cone arrange- 
ment shown at C. A 
blast of hot air is forced 
through the furnace by 
powerful engines. The 
waste gases, which are 
carried off by the pipe 
W, are used to heat the 
blast to a temperature 
of about 600° C. In the 
hottest part of the fur- 
nace a temperature of 
about 1400° C. is prob- 
ably reached. The iron 
is melted, and runs down 
to the bottom of the fur- 
nace at I. The melted 
slag being lighter floats 
upon it, and is drawn off at intervals through the slag hole. 
The crucible, as the lower part of the furnace is called, is 
opened three or four times a day and the iron allowed to 
run out into the sand moulds, forming bars three or four 
inches square and about four feet long, which are known as 
pig iron. When a furnace is in full blast charges are intro- 
duced at the top at regular intervals, and the process often 
continues uninterruptedly for years. 




iron 159 

244. Pig Iron is brittle, crystalline, and easily fusible ; it 
cannot be welded. It is not pure iron, but contains from 
3 % to 6 % of carbon, and varying quantities of silicon, 
phosphorus, sulfur, and manganese. Most of the carbon is 
combined with the iron as a carbid, in what is known as 
white cast iron, whereas in gray cast iron, which is softer 
and more desirable for certain purposes, a large part of the 
carbon in the form of graphite crystals is mechanically dis- 
seminated through the iron. Sulfur and phosphorus are 
objectionable elements in iron, particularly if it is to be 
converted into wrought iron or steel; the sulfur makes it 
"hot short," that is, brittle when hot, and the phosphorus 
makes it " cold short," or brittle when cold. 

245. Wrought Iron is tough, malleable, and fibrous in 
structure; it melts at 1500° C, and as it approaches this 
temperature becomes pasty, in which condition two bars 
may be firmly joined by hammering them together; it con- 
tains less than one-half of 1 % of carbon, cannot be tem- 
pered, and does not retain magnetism. 

Preparation. — Wrought iron was originally prepared di- 
rectly from the pure ore by heating it with charcoal and 
hammering the slag out of the mass; this process was 
known as "blooming." The process by which wrought 
iron is now prepared is termed "puddling." Cast iron 
is placed on the hearth (H) of a reverberatory furnace 
(Fig. 18), which is lined with a layer of ferric oxicl. The 
iron is melted and constantly stirred to expose the impurity 
to the air ; for a time the mass appears to boil, owing to 
the formation of carbon monoxid. As the impurities are 
oxidized, the mass becomes pasty, because of the higher 
melting point of wrought iron ; and the pasty material is 
collected on one side of the furnace and worked up into 



160 



CHEMISTRY 



large lumps or blooms which are passed through rolls to 
remove the liquid slag. The ferric oxid used for the lining 
or fettling assists materially in oxidizing the impurities, 
and the process above described is sometimes called " pig 
boiling" to distinguish it from the "dry puddling" pro- 
cess in which the cast iron requires preliminary refining. 
For interesting history of wrought iron see Roscoe and 
Schorlemmer's Chemistry ', Vol. II, pt. ii, p. 34. 

246. Steel is malleable, has a fine crystalline structure, 
may receive a high polish, may be welded, is easily fusible, 
melting at about 1400° C. Its extensive use depends upon 




the fact that it may be tempered. When heated to redness 
and suddenly immersed in cold water, it is rendered very 
hard and brittle ; if heated and slowly cooled, it is rendered 
soft, and by regulating the temperature at which it is tem- 
X^ered, almost any desired degree of hardness, toughness, or 
elasticity may be obtained. Steel contains from ^ to 2 °/ 
of carbon. 

Preparation. — Steel may be made in three ways: (a) by 
adding carbon to wrought iron (the cementation process), 
(6) by burning out a part of the carbon of cast iron (the 
Bessemer process), and (c) by melting together proper pro- 



IRON 161 

portions of wrought and cast iron (the Siemens-Martin 
process). 

(a) TJie Cementation Process. — Bars of wrought iron are 
packed in charcoal in fire-clay boxes which are kept at a red 
heat for a week or more ; the carbon penetrates the iron, 
giving it a blistered appearance, hence its name blister 
steel. It is not quite uniform in composition, but when 
remelted and cast into ingots this objection is overcome, and 
the crucible steel thus formed is considered the best kind 
for knives, springs, and tools; it is sometimes called cast 
steel. 

(6) The Bessemer Process. — A large, covered, egg-shaped 
crucible, mounted on trunions, called a converter, and 
capable of holding from five to ten tons, is filled with 
melted cast iron. A powerful blast of air is blown through 
the converter, oxidizing the impurities ; the peculiar flame 
of carbon monoxid is observed above the converter, and 
when this disappears, showing that the carbon has all been 
consumed, a definite quantity of speigeleisen, an iron rich in 
carbon, is added, and the mass is thus converted into the 
grade of steel desired. By this process a converter full of 
cast iron has been converted into steel in five minutes. 
This process has reduced the price to such an extent that 
some grades of steel are now sold at a lower price than 
wrought iron. 

(c) The Siemens-Martin Process. — Pig iron is melted in 
an open hearth furnace, and wrought iron and iron ore are 
added in such quantities as to yield a product containing 
the desired percentage of carbon. Toward the close of the 
"melting, which usually lasts eight or ten hours, a sample is 
taken and the percentage of carbon quickly determined by 
the chemist, who directs such changes in the mixture as 
may be necessary to produce the kind of steel desired. 



162 CHEMISTRY 

247. Compounds of Iron. — Like mercury and copper, 
iron forms two series of salts corresponding to the two 
oxids with which the student is already familiar. For ex- 
ample, we have two chlorids, the ferrous, FeCl 2 and the 
ferric, Fe 2 Cl 6 , their properties being entirely distinct. 

248. Compounds of Iron and Oxygen. — Iron forms three 
compounds with oxygen, viz. : — 

Ferrous oxid, FeO 

Ferric oxid, Fe 2 3 

Ferroso-ferric oxid, Fe 3 4 

Ferrous oxid is a black powder which absorbs oxygen so 
rapidly that it takes fire when exposed to the air. When 
dissolved in acids it forms ferrous salts. 

Ferric oxid is one of the important ores of iron. It is 
much used as a pigment in so-called iron paint. Jewellers' 
rouge, used in polishing plate glass and jewellery, is a finely 
ground, artificial ferric oxid; the red rust formed at ordi- 
nary temperatures is a hydrated ferric oxid, 2 Fe 2 3 + 3 H 2 0, 
or a hydroxid, Fe 2 (HO) 6 -+- Fe 2 3 , which absorbs oxygen 
from the air and communicates it to neighboring molecules 
of iron. We can now understand why iron does not rust in 
dry air at ordinary temperatures, and why the process pro- 
ceeds so much more rapidly in moist air after an article 
becomes coated with rust. 

Ferroso-ferric oxid is the richest of the ores of iron ; it is 
attracted by a magnet (hence its common name, magnetite), 
and many specimens are strong natural magnets. The 
magnetic oxid, as it is often called, is formed when iron 
is raised to a high temperature in air. Unlike the hydrated 
ferric oxid, this oxid does not absorb oxygen from the air, 
but serves to protect a mass of iron from further rusting. 
Meteorites acquire a coating of this oxid which protects 



IKON 163 

them from the action of the air. In the Bower-Barff pro- 
cess of producing rustless iron for various ornaments, the 
articles are coated with magnetic oxid by heating them in 
superheated steam or in an oxidizing flame. 

249. Compounds of Iron and Sulfur. — Four compounds of 
these elements are known. 

Ferrous sulfid, FeS, is the most important to chemists, 
being a convenient and inexpensive source from which 
hydrogen sulfid can be obtained. It is a brittle, dark gray 
mass resembling a metal. It is prepared by dipping a white- 
hot wrought iron in melted sulfur, or by strongly heating 
a mixture of three parts of iron and two of sulfur. Exposed 
to the air, it slowly decomposes, forming sulfur dioxid and 
ferric oxid. 

Ferric disuljid, FeS 2 , occurs in nature as iron pyrite which 
is used by certain manufacturers in the process of preparing 
sulfuric acid. 

Ferroso-ferric sulfid, Fe s S 4 , corresponds to the magnetic 
oxid of iron. It is attracted by a magnet, and some speci- 
mens are magnetic. 

Iron sesquisulfid, Fe 2 S 3 , a fourth compound, is unim- 
portant. 

250. Sulfates.— Ferrous sulfate, FeS0 4 + 7 H 2 (green 
vitriol or copperas), is formed when iron is dissolved in 
sulfuric acid ; it is usually manufactured by exposing heaps 
of iron pyrite to the action of the air and moisture at a 
gentle heat. Chemically pure ferrous sulfate forms trans- 
parent bluish green crystals which effloresce when exposed 
to dry air and become covered with a white incrustation. 
Ferric sulfate, Fe 2 (S0 4 ) 3 , resembles aluminum sulfate in that 
it combines with alkaline sulfates to form double sulfates 
or alums. 



164 CHEMISTRY 

Ferrous sulfate is sometimes used as a disinfectant, but 
its chief use is in making black ink in connection with some 
astringent like tannic acid or nutgalls. 

Experiment LXXXL To prepare ink. — Dissolve | gramme of 
tannic acid in 30 cc. of H 2 ; to 22 cc. of this add a few drops of a 
solution of copperas and an equal amount of mucilage ; a pale ink is 
formed which gradually darkens. 

REVIEW QUESTIONS 

1. Name the principal ores of iron. 

2. Describe the manufacture of crucible steel, the manufacture of 
Bessemer steel, and state for what class of purposes each is used. 

3. Distinguish chemically between pig iron and wrought iron. 
Describe the manufacture of each. 

4. Describe three processes by which steel is made. Compare the 
cost of the processes and the value of the products. 

5. Describe the manufacture of the following : (a) cast iron from 
ore ; (b) wrought iron from cast iron ; (c) steel from cast iron ; 
(d) steel from wrought iron. 

6. How does ferrous sulfate differ from ferrous sulfid ? From what 
acid was each obtained, and for what is each used? 



CHAPTER XXIII 
TIN AND LEAD 

TIN 
Symbol Sn. — Atomic Weight 119 

251. Occurrence. — Although tin is not widely diffused in 
nature, it occurs in very large quantities in a few localities, 
viz. in Cornwall, England, and in Saxony. It has recently 
been discovered in South Dakota. It is probable that tin 
does not occur free in nature, although it is reported that 
metallic tin is found in Siberia and Guiana. Tin stone or 
cassiterite, Sn0 2 , is the only ore that is now reduced. 

252. Reduction. — The finely crushed ore is washed free 
from earthy matter, then calcined in a reverberatory furnace 
to expel certain impurities and oxidize others, then washed 
a second time. The ore thus purified is mixed with pow- 
dered anthracite coal, and again heated in the furnace. 

253. Properties. 

Experiment LXXXII. — Examine pieces of tin and lead, noting the 
color, lustre, and hardness of each. Compare the freshly cut surface 
of each with a surface that has been exposed to the air for some time. 
Which metal is the better as a coating to prevent oxidation of other 
metals ? Which is the more easily oxidized ? Which metal is the 
more malleable ? Brittle ? Elastic ? Has either metal a crystalline 
structure ? (To answer this dip a piece of each metal in dilute aqua 
regia.) 

At ordinary temperatures tin is easily beaten into sheets 
known as tin foil. At 200° C. it is brittle and may be 
powdered, and at 228° C. it melts. The crystalline structure 
165 



166 CHEMISTRY 

of tin is often brought out for purposes of ornamentation. 
When a bar of tin is bent, the surfaces of the crystals 
within the bar rub against each other, making a peculiar 
creaking sound known as the "tin cry," and a perceptible 
increase in temperature at the point of flexure may be caused 
by bending a bar backwards and forwards a few times. 
Ordinary tin plate, or in common parlance, tin, is thin sheet 
iron coated with a film of tin by dipping it in a bath of the 
molten metal. A cheaper variety, called terne plate, used 
for roofing, and sometimes for cheaper tinware, is coated 
with an alloy of tin and lead. Such ware should never 
be used for cooking or for making cans for preserving fruits 
and vegetables, because the acids of the foods may form 
poisonous compounds with the lead. 

254. Alloys. — Tin forms a large number of useful alloys. 
Pewter contains three parts of tin to one of lead. 
Britannia metal contains tin 84 parts, antimony 10 parts, 

copper 4 parts, and bismuth 2 parts. 

Soft solder contains equal parts of tin and lead. 

Bell metal and bronze are alloys of copper and tin, and the 
" fusible metals," some of which will melt in boiling water, 
are usually alloys of tin, bismuth, lead, etc. 

Among the important alloys which do not contain tin, 
the following may be mentioned : Brass contains 1 part 
copper and 2 parts zinc ; German silver is brass whitened 
with nickel; coin silver is silver with 8 to 10 parts of 
copper; gold coin consists of gold with 8 to 10 parts of 
coin silver; aluminum bronze contains aluminum ( .) parts 
and copper 1 part. All alloys melt at a lower tempera- 
ture than that of either constituent. 

255. Compounds. — Tin forms two series of compounds: 
the stannic, in which the atom is quadrivalent, and the 



TIN AND LEAD 1(37 

stannous, in which it is bivalent. Beside the stannic 
oxid, Sn0 2 , which occurs in nature, stannous oxid, SnO, 
is known; it is a black substance soluble in acids, form- 
ing stannous salts. The best known compounds of tin 
are the chlorids. Stannous, SnCl 2 , is an excellent reducing 
agent, and is used by dyers. The tin salt of commerce 
is a crystalline stannous chlorid, SnCl 2 + H 2 0. Stannic 
chlorid, SnCl^ is also used by dyers. Stannic sulfid, SnS 2 , 
is a golden yellow crystalline substance, and is largely 
used as a pigment under the name of mosaic gold. 

LEAD 
Symbol Pb. — Atomic Weight 207 

256. Occurrence. — The few specimens of metallic lead 
which have been found free in nature were probably formed 
by the reduction of ores of lead by volcanic action. In 
combination it occurs in enormous quantities; the most 
abundant compounds are the sulfid, PbS, known as gale- 
nite, and the carbonate, PbC0 3 , known as cerussite. The 
sulfate and the chlorid also occur in considerable quan- 
tities. Nearly all the lead of commerce is obtained from 
the sulfid. Small quantities of the sulfid are found in 
New York State, in the Niagara limestone. 

257. Reduction. — Lead is easily reduced from its ores. 
It was one of the seven original metals of the ancients. 
The richer ores are heated to a dull red heat on the hearth 
of a reverberatory furnace. Sulfur dioxid is given off, and 
there remains a mixture of lead oxid, lead sulfate, and 
lead sulfid. The air is now shut off and the temperature 
raised, converting the above compounds into metallic lead 
and sulfur dioxid. About 10% of the lead remains in the 
furnace, mixed with the slag; this may be recovered by 



168 CHEMISTRY 

the process described below. The poorer ores are heated 
in a small cupola or blast furnace, with coke and metallic 
iron or ferrous silicate. Iron sulfate is formed, the lead 
is reduced and is drawn off at the bottom of the furnace. 

258. Properties and Uses. 

Experiment LXXXIII. — Grind a little oxid of lead with a few 
cubic centimetres of water in a mortar, filter, and test for lead with 
hydrogen sulfid. Is lead oxid soluble ? Is lead suitable for pipes in 
which to convey drinking water ? 

All soluble salts of lead are poisonous. Write a brief 
account of the properties of lead shown by Experiment 78. 

Lead is extensively used for water pipes, for plates of 
storage batteries, in making shot, in preparing white lead, 
and in various alloys. 

259. Compounds. — Lead forms five oxids having the 
following formulas : Pb 2 0, PbO, Pb 2 3 , Pb 3 4 , Pb0 2 . Of 
these, litharge, PbO, and red lead, Pb 3 4 , are the most impor- 
tant. Eed lead is extensively used as a pigment, and in 
the manufacture of flint glass for lenses, cut glassware, etc. 
The dioxid, Pb0 2 , a chocolate colored powder, is an excellent 
oxidizing agent. It is formed on the positive electrode of 
a storage battery during charging. White lead, which forms 
the basis of most paints, is a basic carbonate, having the 
formula 2PbC0 3 , Pb (OH) 2 . Lead chromate, PbCr0 4 , com- 
monly known as chrome yellow, is also used as a pigment. 

REVIEW QUESTIONS 

1. Describe the physical properties of lead. 

2. What are the chief ores of lead ? 

3. What compounds of lead are used as pigments ? 

4. What are the chief properties of tin ? 

5. What is tin plate ? What are its advantages over iron plate ? 
Over Terne plate ? 

6. From what ores is tin obtained ? 



CHAPTER XXIV 
PLATINUM 

Symbol Pt. — Atomic Weight 194.9 

260. Occurrence. — Platinum is invariably found uncom- 
bined in nature, and is usually associated with the related 
metals, osmium, iridium, paladium, etc. Most of the plati- 
num of commerce is obtained from the Ural Mountains, 
but small quantities are found in California, Australia, and 
Brazil. 

261. Preparation. — The ore is treated with aqua regia, 
which does not dissolve osmium and iridium ; the solution 
is treated with ammonium chlorid, which precipitates a 
double chlorid of ammonium and platinum. This is ig- 
nited, driving the chlorin and ammonium off, and leaving 
a spongy mass known as platinum sponge. 

262. Properties. 

Experiment LXXXIV. — Examine a piece of platinum, noting its 
color, malleability, and specific gravity. Heat a piece in the Bunsen 
burner. Does it melt ? Is it oxidized in the flame ? Endeavor to 
fuse a bit of platinum wire into a glass tube ; try other kinds of wire. 
Why is platinum used in incandescent lamps ? Is it soluble in any 
of the ordinary acids ? Save any salts formed. 

263. Uses. — The properties shown above make platinum 
a very useful article to the chemist; platinum wire, foil, 
crucibles, and various other utensils are in constant use 
in every laboratory. Its permanence in air leads to its 
use for small weights, and it is exclusively used in incan- 
descent lamps and other apparatus in which an electric 
current is to be conducted through glass. 

169 



PART II 

CHAPTER XXV 
CARBON 

Symbol C. — Atomic AVeight 12 

264. Occurrence. — This important element occurs free in 
nature in each of its three allotropic forms, viz. the diamond, 
graphite, and charcoal ; combined with oxygen as carbon 
dioxid, it occurs in the atmosphere and in many mineral 
waters, also in limestone, marble, and all carbonates. All 
living things contain carbon. In the animal kingdom it is 
usually combined with hydrogen, oxygen, and nitrogen, and 
in the vegetable kingdom with hydrogen and oxygen. 

The number of carbon compounds formed in the life 
processes of plants and animals is almost infinite, and it was 
once believed that these compounds could not be formed in 
any other way, that they possessed some peculiarity of 
molecular structure due to the action of vital force, and, 
therefore, could not be prepared by laboratory processes ; 
these compounds were distinguished as organic substances, 
and those which could be prepared without the aid of vital 
force were called inorganic substances. There is now no 
good reason for maintaining this distinction except the great 
number of compounds and the similarity of their properties. 
It is quite likely, however, that for these reasons the terms 
170 



CARBON 171 

" organic chemistry" and "inorganic chemistry" will be 
retained, but the old meaning is gone ; and now organic 
chemistry may be defined as the chemistry of the carbon com- 
pounds. 

265. The Diamond. — Diamonds are found in the East 
Indies, Brazil, Mexico, Australia, Africa, Borneo, and Suma- 
tra. There is some evidence that diamonds exist in other 
celestial bodies, as they have been recently found in 
meteors. The diamond is the hardest substance known, 
and can be ground and polished only with its own dust. 
When polished it has a magnificent lustre, and its high 
refractive power causes it to sparkle and show varied 
colors, although the gem itself is generally colorless. Its 
beauty and rarity make it the most precious of gems (the 
Kegent diamond is valued at $ 500,000). If heated to a 
high temperature, it swells up and is converted into a sub- 
stance resembling graphite, which burns, forming carbon 
dioxid. In 1814, Sir Humphry Davy proved that carbon 
dioxid was the only product of the combustion of a diamond, 
thus proving that it was pure carbon. 

Uses. — It is used as a gem; by the glazier in cutting 
glass ; in the diamond drill for boring rocks and other hard 
substances. Its powder is used in grinding and polishing 
gems of all kinds. 

266. Graphite is familiar as the "black lead" of the mis- 
named "lead pencil." It is found abundantly in nature, 
large beds occurring at Ticonderoga, N.Y., and famous ones 
in Siberia and on the island of Ceylon. It occurs both in 
the crystalline and amorphous forms, but its crystals are not 
the same shape as those of the diamond. Ordinary coke 
or charcoal is converted into graphite when heated in the 



172 CHEMISTRY 

arc light. About a quarter of an inch of the end of a carbon 
from an electric lamp is always an impure graphite. Con- 
siderable graphite has been formed as a by-product in the 
process of making carborundum in an electric furnace, and a 
company has now been formed to manufacture graphite by 
the Acheson process, in which powdered graphite mixed 
with certain oxids is passed in a continuous stream through 
an electric furnace, which converts it into a high grade of 
graphite. The inventor believes that the coke first combines 
with the metal of the oxid, forming a carbicl, and that as the 
temperature rises, the carbid is decomposed and the metal 
volatilized, leaving a pure graphite. 

Properties. — Graphite is opaque, has a grayish color and 
a metallic lustre ; it is very friable, is quite soft, leaving a 
mark on paper, hence its name ; it is insoluble in all known 
liquids, is a good conductor of both heat and electricity, and 
is smooth and slippery to the touch. It is permanent in air 
at ordinary temperatures, but burns, forming carbon dioxid, 
when raised to a high temperature. 

Uses. — Graphite is used in making lead pencils and 
crucibles for molten metals, as a lubricant, as stove polish, 
for foundery facings (to secure smooth castings), in the 
process of electrotyping, and in paint. 

267. Amorphous Carbon. — The amorphous varieties of 
carbon are almost always obtained by charring some organic 
substance, i.e. by burning it in a limited supply of air. The 
hydrogen and the volatile compounds are burned, leaving 
the amorphous carbon. The principal varieties of amor- 
phous carbon are charcoal, lampblack, gas carbon, and 
animal charcoal. 

268. Charcoal. — The ancient way of " coaling wood," as 
the process is still called, is carried on as follows : In the 



CARBON 173 

centre of a carefully levelled piece of ground, termed the 
" hearth. " or " earth/ 1 ' a centre pole is erected, and around 
this the wood is piled, forming a flattened cone. This is 
covered with earth, the centre pole is withdrawn, leaving a 
"chimney," at the bottom of which the fire is kindled. 
During the early stage of the process much smoke and flame 
formed by the combustion of the volatile matter issues from 
the top of the pile. As soon as this disappears, all vents are 
closed and the mass allowed to cool. In this process there 
is great liability to loss through the admission of too much 
air, and the by-products are all wasted. 

Retort Charcoal. — In this process the wood is heated in 
retorts from which air is excluded, thus preventing combus- 
tion of the charcoal. The liquids driven off, consisting of 
tar, pyroligeneous acid, wood alcohol, acetone, benzol, etc., 
are collected in suitable condensers, and the gases liberated, 
which consist mainly of marsh gas, hydrogen, carbon mon- 
oxid, and acetylene, are used in heating the retort; small 
wood and sawdust can be charred by this method. 

269. Properties of Charcoal. 

Experiment LXXXV. — Carefully measure and weigh a small piece 
of dry pine, place it in a test tube and cover it with dry sand ; apply 
heat as long as gas is evolved. Is the gas combustible ? When the 
evolution of gas ceases, set the tube aside to cool ; empty the tube and 
examine the sand. Is there any evidence that either of the liquid 
products was retained by the sand ? Which ? Measure and weigh 
the charcoal. How do the linear dimensions compare with those of 
the wood used ? How does the volume compare ? Examine with a 
glass to determine whether the grain of the wood is preserved. Twist 
a small wire about a piece of charcoal and hold it in the Bunsen 
burner flame until ignited ; does it melt ? does it burn with a flame ? 
Why does wood burn with a flame ? Is charcoal soluble in acids ? 
in alkalies ? 

Experiment LXXXVL Filters. — Place about a teaspoonful of 
animal charcoal in a test bottle ; fill the bottle nearly full with a 



174 CHEMISTRY 

solution of potassium permanganate ; shake the bottle vigorously, then 
pour the contents on a filter. What is the color of the liquid ? What 
property does charcoal possess that renders it useful in niters ? 

Experiment LXXXVII. Charcoal as a Deodorizer. — Into the 
neck of a funnel thrust a bit of cotton and cover it to a depth of two or 
three centimetres with powdered charcoal ; through this filter pass a 
quantity of water charged with hydrogen sulfid, and observe. 

Experiment LXXXVIII. Carbon as a Reducing Agent. — 1. Mix 
two or three grammes powdered copper oxid, CuO, and about ^ 6 its 
weight of powdered charcoal ; heat in an ignition tube fitted with an 
outlet tube. Pass the gas which is given off into clear lime-water 
contained in a test tube. What is the appearance of the substance left 
in the tube ? Does it suggest the metal copper ? 

2. Treat a little with strong nitric acid. What should take place if 
the substance were metallic copper ? (Refer to process of making 
nitric oxid.) What does take place ? What is the reaction which 
takes place between the copper oxid and the charcoal ? Write the 
equation. 

Experiment LXXXIX. Products of the Combustion of Carbon. — 
Twist a bit of wire about a small piece of charcoal, hold it in the flame 
of a Bunsen burner until it is well ignited, then insert it in a test bottle 
containing a little lime-water. Cover the bottle with the hand for a 
minute, remove the charcoal, and shake the bottle. What occurs ? 
What compound is formed by the combustion of charcoal ? 

Experiment XC. (Performed by Teacher.) — Collect a bottle of 
ammonia gas over mercury. Heat two or three lumps of charcoal to 
redness and pass them through the mercury into the ammonia. What 
Dccurs ? Estimate the relative volumes of the charcoal and the gas. 

Experiment XCI. Does Charcoal Float? — Drop a piece of char- 
coal in a glass of water and place the glass under the receiver of the 
air pump. Exhaust the air. Explain. 

At ordinary temperatures the chemical energy of charcoal 
is exceedingly feeble. It is, therefore, one of the most dur- 
able of substances. It is frequently found in prehistoric 
fireplaces in a very perfect state of preservation. The 
charred grain found in the excavations at Pompeii is as fresh 
as if burned yesterday. The charcoal carbonized at about 
300° is a soft, brownish black substance igniting at about 



CARBON 175 

380° while that carbonized at high temperatures is dense 
and difficult to ignite. The absorption and condensation of 
gases by charcoal is due to so-called surface action, i.e. to 
the adhesion between the molecules of the gas and the 
charcoal. It is probable that in the case of the easily 
liquefiable gases a portion of the gas is condensed to the 
liquid state by this action (a phenomenon which should 
increase the temperature of the carbon). 

The condensed gases manifest marked chemical activity, 
for example, hydrogen and chlorin combine even in the 
dark when absorbed, and absorbed hydrogen sulfid is so 
rapidly oxidized when charcoal containing it is placed in 
oxygen as to ignite the charcoal. This property explains 
the action of charcoal as a disinfectant. The atmospheric 
oxygen which is condensed in the pores of the charcoal 
oxidizes the offensive and injurious gases. Charcoal has 
been known to absorb 170 volumes of dry ammonia. 

Uses. — The amorphous varieties of carbon are extensively 
used as reducing agents as in the processes of smelting, in 
which ores are reduced to metals by heating them with 
some form of carbon and in the Leblanc process. Charcoal 
is used in niters, as a disinfectant, and for kindling purposes. 

270. Lampblack. 

Experiment XCIL — Close the holes at the base of a Bunsen burner, 
and hold a piece of cold metal in the flame. Examine the deposit of 
lampblack formed. Describe it. 

On a large scale lampblack is prepared by burning sub- 
stances rich in carbon in a limited supply of air. The 
dense smoke formed passes through chambers in which 
coarse blankets are suspended, and on these the soot collects. 

Uses. — Great quantities of lampblack are used in the 
manufacture of printer's ink, paints, and electric light 
carbons. 



176 CHEMISTRY 

271. Animal Charcoal. — Boneblack, as this substance is 
sometimes called, is prepared by carbonizing bones in iron 
retorts. It contains about 10 % of carbon, but it possesses 
many of the valuable properties of charcoal in a marked 
degree, because the carbon is disseminated throughout the 
porous mass of calcium phosphate, which forms about 88 % 
of the mass. 

Uses. — Sugar refiners use animal charcoal filters to 
clarify solutions of raw sugar, and oil refiners also use it 
to decolorize the better grades of lubricating oils. 

272. Relative Kindling Temperature of Carbon and Hydro- 
gen. — The kindling temperature of hydrogen is probably 
between 500 and 600° C, and that of carbon is very much 
higher. One of the results of this difference in kindling 
temperature was seen in Experiment 92, in which the flame 
of a fuel composed of hydrogen and carbon was cooled 
below the kindling temperature of carbon, and the carbon 
was no longer consumed, a part of it was deposited on the 
metal, and the balance escaped as smoke. All smoky flames 
may be attributed to the fact that the temperature of a 
portion, or possibly the whole of the flame, is below the 
kindling temperature of carbon; and the smoke would dis- 
appear or would be "consumed" if the temperature of the 
flame should be raised so that all parts should be above the 
kindling temperature of carbon. 

A second effect of this difference in kindling temperature 
is shown in the facility with which certain fuels may be 
kindled. When a fuel containing carbon and hydrogen is to 
be kindled, it is only necessary to supply sufficient heat to 
raise it to the temperature at which it evolves hydrogen, or 
some compound of hydrogen and carbon, and to kindle the 
evolved gas ; whereas if the fuel is a pure carbon it must be 



CARBON 177 

raised to a much higher temperature before it "takes fire." 
This explains the ease with which wood or soft coal is 
kindled as compared with hard coal or coke. 

In the process of making water gas it is found that at 
the high temperature of the anthracite fire, carbon mani- 
fests sufficient energy to take oxygen away from hydrogen, 
whereas we now find that at certain lower temperatures 
hydrogen combines with oxygen and carbon does not. 
Few better illustrations of the effect of heat upon chemi- 
cal energy have been suggested. 

273. Smoky Flames. — The temperature attained by a 
flame depends upon the rate at which the fuel is con- 
sumed, and upon the rate at which the heat escapes. 

As already illustrated in several processes, the rate of 
combustion of fuel may be controlled by regulating the 
amount of air supplied ; when too little air is supplied the 
flame is cooled, and this is one of the chief causes of smoky 
flames. 

As has already been shown, smoky flames are sometimes 
due to chilling the flame by contact with cold objects. If 
the cold object is a good conductor of heat, the effect con- 
tinues a longer time, as is noticed when one builds a fire in 
a cold stove. 

A third cause of smoky flame is the presence of moisture 
in the fuel, a large amount of heat is withdrawn from the 
flame to vaporize the moisture, thus lowering the tempera- 
ture. To this cause the great volume of smoke noticed 
when green wood or grass is burning is due. 

274. The Instability of Organic Substances. — A number 
of causes combine to make organic compounds less stable as 
a rule than inorganic compounds. 



178 CHEMISTRY 

(a) The chief cause undoubtedly lies in the fact that 
carbon compounds are subject to the attacks of micro- 
organisms. To this cause we must attribute all cases of 
putrefaction and decay. Both animals and plants require 
carbon, and their food is principally composed of substances 
containing carbon, but certain carbon compounds, like car- 
bolic acid and some of the organic poisons, are not attacked 
by microorganisms. 

(b) Some of the most unstable of the organic compounds 
owe their instability to the presence of nitrogen. The feeble 
affinity which characterizes the nitrogen atom renders the 
decomposition of the substance containing it less difficult 
than it would be if some more active element replaced the 
nitrogen ; hence most animal products are unstable. 

(c) All organic compounds are endothermic; and endo- 
thermic substances are less stable than exothermic, because 
they do not require the expenditure of energy to effect their 
decomposition. 

(d) The elements found in organic compounds differ 
widely in valence ; carbon is quadrivalent, oxygen is biva- 
lent, nitrogen trivalent, and hydrogen univalent, thus ren- 
dering a greater number of combinations possible than 
could be formed if they were all of the same valence. We 
thus have many organic compounds of the same elements 
which are easily changed into kindred forms. 

(e) The molecules of many organic compounds are ex- 
ceedingly complex, sometimes containing more than 100 
atoms, united in various sub-groups, or radicals, to form 
the molecule. The energy required to bring about a re- 
arrangement of these radicals in the molecule, or the elimi- 
nation of one or more radicals, is less than that required to 
decompose simpler molecules, and they are therefore less 
stable. 



CARBON 179 

275. Use of Organic Substances as Fuels. — All organic 
things are endothermic, i.e. they develop heat when they 
combine with oxygen. The quantity of heat developed by 
the oxidation of carbon and hydrogen is greater than that 
developed by any other elements, and for this reason 
organic substances are particularly valuable as fuels. 
Another decided advantage lies in the fact that the 
products of the combustion are in the aeriform state when 
formed, and are therefore easily carried away by the draft 
of the chimney. 

REVIEW QUESTIONS 

1. Why do we char fence posts and telegraph poles ? 

2. Show why lamp chimneys are used. Why is gas flame spread 
out like a bat's wing ? 

3. Why is air introduced in the centre of the flame of the 
"Rochester burner" ? 

4. Why is more smoke seen to issue from a chimney on starting 
a fire than after it has burned for a time ? 

5. Why is a curling iron blackened when held in the gas flame ? 

6. Discuss the chemical energy of charcoal. 

7. Describe an experiment to demonstrate that the diamond is a 
form of carbon. 

8. Compare the charring of wood by fire with the charring of 
wood by acid. 

9. In what respects are charcoal filters better than other kinds for 
purifying drinking water? If a porous stone or porcelain filter is 
used, what may be done to attain the same end as that attained by 
the use of the charcoal filter ? 

10. Discuss the use and care of a charcoal filter as compared with 
the use and care of some other filter. 

11. How does charring of wood protect the wood from decay ? 
How does charging wood with creosote affect its liability to decay ? 

12. Show why utensils used over a wood fire are generally more 
blackened than those used over a coal fire. 

13. Can you build a bonfire of anthracite coal as you build one of 
dry wood ? Give reason for your answer. 

14. What causes a fire to smoke ? State two methods employed to 
overcome this difficulty. 



180 CHEMISTRY 

15. From what country does the graphite used in Faber pencils 
come ? in Dixon pencils ? (Consult legend on pencil.) 

16. What can you say of the affinity of charcoal for oxygen at 
high temperatures ? How does it compare with the affinity of other 
substances for oxygen at high temperatures ? 

17. Discuss the shrinkage of wood when carbonized. 

18. Describe and explain the combustion of charcoal. 

19. Does turning a lamp wick up affect the air supply ? Why does 
raising the lamp wick cause the lamp to smoke ? 

20. Explain why wood is ignited at a lower temperature than coal. 



CHAPTER XXVI 
CARBON AND OXYGEN 

SECTION I. —CARBON DIOXID 
Formula CO2. — Molecular "Weight 44 

276. Occurrence. — This gas is a constant constituent of 
the atmosphere, to which it is supplied- by the respiration 
of animals, and by combustion and decay. It is found in 
all spring waters, and issues from the earth in many places. 
The Poison Valley in Java and the Grotto del Cane near 
Xaples owe their properties to the carbon dioxid, which is 
supplied from subterranean sources. Old wells are fre- 
quently filled with it. 

In combination with bases, carbon dioxid occurs in large 
quantities ; e.g. limestone, marble, etc. 

277. Preparation. 

Experiment XCIII. To prepare carbon dioxid, and to determine 
certain of its properties ; (a) color, (6) odor and taste, (c) weight, 
{d) solubility, (e) combustibility. — In the generating bottle place 
eight or ten lumps of marble or chalk (not prepared crayons) . Cover 
the lumps with water, and add a small quantity of hydrochloric acid. 
Collect several bottles of the gas by downward displacement. 

1. Lower a lighted taper into a bottle of the gas, and observe. 
Now introduce a burning stick into the same bottle. 

2. Place a lighted taper in an empty bottle, and pour the contents 
of the second bottle of gas upon the flame, proceeding as if pouring 
water. 

3. Pour some of the gas into a bottle containing lime-water ; shake 
the bottle ; this is the test for carbon dioxid. 

181 



182 CHEMISTRY 

4. Prove that the gas may be transferred by pouring from one 
vessel to another. 

5. Is carbon dioxid soluble in water ? Explain the results obtained, 
and state the properties of carbon dioxid illustrated by each section of 
the experiment. Complete the following reaction : — 

CaC0 3 + 2 HC1 = C0 2 + 

Experiment XCIV. — Object : To determine what acids, if any, will 
decompose carbonates. The test for carbonates. — 1. Place as much 
sodium acid carbonate as you can take up on the blade of a penknife 
in a test tube. Arrange a short delivery tube. 

2. Cover the carbonate with dilute sulfuric acid. 

3. Jf a gas is evolved, pass it through lime-water. What is it ? 

4. Repeat the experiment, using (a) hydrochloric acid ; (&) acetic ; 
(c) any weaker acid. Which acids decompose carbonates ? What 
substances evolve carbon dioxid when treated with an acid ? 

Experiment XCV. Object : To investigate the direct combination 
of carbon dioxid with bases. — 1. Fill a test bottle one-fourth full of a 
solution of sodium hydroxid. 

2. Pass carbon dioxid through the solution as long as it is absorbed. 

3. Add acid to a portion of the solution. 

4. Devise a test which will prove what gas is evolved. 

5. Write the reactions which occur when the gas is passed through 
the solution, and when the acid is added. 

Experiment XCVI. Object: To determine why lime-water is ren- 
dered turbid by carbon dioxid. — 1. Collect some of the white insolu- 
ble substance formed by passing carbon dioxid through lime-water on 
a filter. 

2. Treat the white precipitate with dilute acid. What evidence 
have you that it is calcium carbonate ? How was the carbonate 
formed ? 

278. Physical Properties. — Your experiments have shown 
you the color, odor, taste, solubility, and weight of this gas. 
At ordinary temperatures and pressure, water dissolves 
about its own volume of carbon dioxid. As pressure is 
increased, the solubility increases ; this fact is illustrated 
in the ordinary aerated waters. Water under a pressure of 
several atmospheres is saturated with the gas, and when 
the pressure is reduced to one atmosphere by withdrawing 



CARBON AND OXYGEN 183 

the cork, or by drawing a glassful from a fountain, the 
excess of gas dissolved at the higher pressure is liberated, 
causing the familiar effervescence. At — 5° C. carbon dioxid 
is liquefied by a pressure of about 31 atmospheres ; under 
ordinary pressures it boils at — 87° C. It is a colorless, 
mobile liquid, which floats on water without mixing with it. 
Liquid carbon dioxid is prepared on a large scale by com- 
pressing the gas evolved in the process of brewing, in steel 
cylinders ; in this form it is largely used by manufacturers 
of aerated waters. When liquid carbon dioxid is allowed 
to escape into air, the absorption of heat due to rapid 
evaporation causes a portion of the liquid to solidify. The 
solid carbon dioxid is a soft, white, snow-like substance. It 
is now an article of commerce known as carbonic acid snow. 

279. Chemical Properties. — The solution of carbon dioxid 
in water is feebly acid, and may be regarded as the true 
carbonic acid. C0 2 + H 2 = H 2 C0 3 . That all carbon dioxid 
dissolved in water is not chemically combined with it is 
shown by the fact that a freshly prepared sample of aerated 
water effervesces more briskly than those that have long 
been preserved. Thus Apollinaris water, when opened, 
effervesces very little, while when gently heated it gives off 
a rapid stream of gas. Such waters have in all probability 
been exposed to pressure for a long time, and the dissolved 
carbon dioxid has almost entirely combined to form carbonic 
acid. 

In the test for carbon dioxid (Experiment 93) the turbid- 
ity was due to the formation of the insoluble calcium 
carbonate. 

CaH 2 2 + C0 2 = CaC0 3 + H 2 0. 

Let us repeat this experiment to illustrate another prop- 
erty of carbon dioxid. 



184 CHEMISTRY 

Experiment XCVII. — Pour a small quantity of lime-water into a 
test tube ; pass carbon dioxid through it for some minutes. Does the 
turbidity increase at first ? Does it continue to increase, or is a point 
reached where all the calcium is converted into calcium carbonate ? 
Continue the supply of carbon dioxid until the liquid becomes clear. 
Now expel the excess of carbon dioxid by boiling the liquid. What 
occurs ? Is calcium carbonate soluble in water containing carbon 
dioxid ? If still in doubt, pass carbon dioxid through some water, 
and pour it into a test tube containing calcium carbonate prepared as 
above. 

The fact that water containing carbon dioxid will dis- 
solve calcium carbonate accounts for the hardness of 
natural waters in limestone regions, and also for the for- 
mation of caves in limestone; and the precipitation of the 
dissolved calcium carbonate, when the carbon dioxid is 
given off, causes the formation of the so-called scale in 
tea-kettles and steam boilers, the formation of stalactites 
and stalagmites in caves, and the deposits of petrified 
moss, or travertine, near certain springs. 

280. Why Carbon Dioxid does not support Combustion. — 

Although carbon dioxid contains more than three times as 
much oxygen as the air, it does not support ordinary com- 
bustion, for it is itself a product of combustion, and as 
should be inferred from the chemical energy manifested 
when carbon dioxid is formed, the elements have a strong 
affinity for each other. Metallic potassium, sodium, and 
magnesium are among the few elements w r hich have a suffi- 
ciently strong affinity for oxygen to take it from carbon, and 
at high temperatures carbon dioxid supports the combustion 
of these substances. 

Experiment XCVIII. — Light a strip of magnesium ribbon, and 
thrust it into a bottle of carbon dioxid. Describe the action. What 
becomes of the carbon of the C0 2 ? Test a small piece of the sub- 
stance into which the ribbon is converted with dilute hydrochloric acid 
to determine whether it is an oxid or a carbonate. Write the reaction. 



CARBON AND OXYGEN 185 

The efficiency of the fire extinguisher and the " chemical " 
fire engines depends upon the fact that carbon dioxid does 
not support combustion. These devices consist of two recep- 
tacles, a larger containing a solution of sodium acid car- 
bonate, and the smaller a few ounces of sulfuric acid. The 
receptacles are usually so arranged that the liquids may be 
mixed by inverting the extinguisher. Carbon dioxid is 
generated, and water charged with the gas is forced out, 
extinguishing any moderate conflagration. 

281. Growth. — One of the broad differences between 
living and dead matter is in the manner of growing. All 
living organisms grow because of the multiplication of cells 
within the body of the organism ; while inert matter is either 
subject to disintegration, or as in the case of the crystal, 
grows by the addition of similar molecules to the outside. 
The growth of the plant differs from that of the animal, in 
that plants constantly increase in bulk by addition to their 
store of organic matter, while animals expend a large per- 
centage of the material which they receive in replacing the 
tissues worn out by the activities of life. 

Experiment XCIX. To determine ivhat gas plants evolve. — 
1. Place a growing plant in a shallow vessel and cover it with a 
stoppered bell jar. 

2. Pour enough water into the vessel to prevent the escape of gas 
from the bell jar, and fill the bell jar with carbon dioxid. 

3. Set the apparatus in the sunlight for a few hours. 

4. Test the gas in the jar for carbon dioxid by lowering a lighted 
taper into it. Is the taper extinguished ? Has anything replaced the 
carbon dioxid ? If so, what ? 

5. Repeat the experiment, having air instead of carbon dioxid in 
the bell jar, and covering it with a heavy cloth or otherwise excluding 
all light. 

6. After a few hours test the air in the jar for carbon dioxid by 
dipping out a bottle full and testing it with lime-water, also by lower- 
ing a lighted taper into the jar. Explain any change that you note in 



186 CHEMISTRY 

composition of the air. What gas is absorbed by plants in the light ? 
In the dark ? What gas is evolved in each case ? 

282. The Life Processes of Plants and Animals. — Plants 
live on inorganic substances, chiefly carbon dioxid, water, 
ammonia, and salts; the carbon dioxid is absorbed from 
the air by the leaves, and the other substances are derived 
from the soil. The carbon dioxid and water are reduced by 
the action of sunlight, and the carbon and hydrogen thus 
liberated combine with oxygen to form starch, C 6 H 10 O 5 , with 
a reaction which is perhaps expressed by the following 
equation : — 

6 C0 2 + 5 H 2 = C 6 H 10 O 5 + 12 0. 

There can be no doubt that the chemical energy which 
effects the decomposition of the carbon dioxid is derived 
from the sunlight; and it is equally certain that chloro- 
phyll, the green coloring matter of the plant, is necessary 
to the reaction, but the part played by the chlorophyll is 
not known. The twelve atoms of oxygen liberated by the 
formation of one molecule of starch are returned to the air. 

Animals are unable to produce the complex organic mat- 
ter required to renew their bodies ; they therefore depend 
either directly or indirectly upon plants for their food. In 
the animal body this organic matter is oxidized and ex- 
haled as carbon dioxid and water, a process which main- 
tains the high temperature of the animal. It thus appears 
that the heat as well as the energy possessed by an animal 
is developed by the combustion of portions of his own body 
by means of oxygen supplied to the air by plants, and that 
the material consumed can only be renewed by foods pro- 
duced by plants. 

The process of respiration in both plants and animals 
consists in the absorption of oxygen from the air, the oxida- 



CARBON AND OXYGEN 187 

Hon of portions of their tissues, and the release of carbon 
dioxid and water. The process is the opposite of assimila- 
tion, in which plants reduce carbon dioxid and exhale oxy- 
gen ; but it occurs at all times, even at daylight, when it 
is overshadowed by assimilation. The quantity of carbon 
dioxid evolved in twenty-four hours by the respiration of a 
given plant is only a small fraction of that assimilated by 
the plant in the same time. 

283. Purification of the Air. — Careful analyses of such 
samples of bottled ancient air as have been found fail to 
show an appreciable difference between the air which the 
ancients breathed and that of to-day. The vegetable king- 
dom has been able to reduce the carbon dioxid poured into 
the air by the oxidation of thousands of tons of animal 
matter and by the combustion of thousands of tons of fuel, 
and to return to the air practically all of the oxygen taken 
from it. 

This reciprocal relation of the life processes of plants and 
animals may be nicely illustrated in a small way by supply- 
ing an aquarium with such proportion of plants and animals 
that the amount of oxygen evolved by the plants shall just 
equal the amount absorbed by the animals, thus rendering 
the renewal of the water unnecessary. Although this action 
of plants is the only means of supplying oxygen to the air, 
it is not the only means employed by nature to keep the 
composition of the air constant and to remove harmful 
impurities therefrom. 

During the colder months of the year, when the quantity 
of carbon dioxid received by the air is greater than at any 
other time because of the increased consumption of fuel, 
the action of plants in this latitude is practically suspended, 
and the amount of carbon dioxid in the air would increase 



188 CHEMISTRY 

were it not for the action of the winds and for the ten- 
dency toward equal distribution of gases known as the 
property of diffusion. The rain is an important agent in 
the removal of impurities, dissolving carbon dioxicl, nitric 
acid, ammonia, and all soluble substances ; and washing 
down germs, dust, soot, and organic matter exhaled by 
animals. 

Sunlight also destroys germs, and to a certain extent pre- 
vents the pollution of the air by drying up damp places' or 
stagnant pools. 

284. Ventilation. — The putrid organic matter exhaled 
from the lungs and discharged through the pores of animals 
is much more harmful than the carbon dioxid which accom- 
panies it ; still the amount of carbon dioxid in the air may 
be taken as an index of the impurity of the air, for the two 
substances are given off by the lungs in proportional quan- 
tities. It is a well-established fact that air which is con- 
taminated by the products of respiration acts as a poison to 
those who breathe it, but the subject of ventilation has not 
yet received the study which its importance demands, and 
our knowledge of the subject is in a somewhat chaotic state. 
The most that can be said at present is, good ventilation 
requires an inlet for fresh air, an outlet for impure air, and 
some means of setting the air in motion. In cases of 
" natural " ventilation, or those in which no special appli- 
ance is employed to cause the circulation of the air, let the 
outlet be at the upper part of the room ; but no system of 
natural ventilation has yet been devised which can be de- 
pended upon in all conditions of wind and weather. The 
system of artificial ventilation which gives most satisfac- 
tory results requires some mechanical means of forcing the 
air through the rooms. 



CARBON AND OXYGEN 189 

SECTION II. — CARBON MONOXID 
Symbol CO. — Molecular Weight 28 
Caution. — Do not inhale this gas. 

285. Preparation. 

Experiment C. — In a large Florence flask place 3 grammes of finely 
powdered potassium ferrocynid and 25 grammes of strong sulfuric 
acid. Heat gently over wire gauze ; remove the burner as soon as 
gas is evolved rapidly. Collect two bottles over water. 

1. Test the inflammability of the gas. 

2. Thrust a lighted splinter into the gas and observe. 

3. When the gas is pure, remove the delivery tube from the flask 
and connect the bent glass tube in its place and ignite the gas as it 
flows from the tube ; observe the characteristics of the flame. 

4. Hold a cold dry bottle over the burning jet. 

5. Pour a little lime-water into the bottle and shake it. What is 
the product of the combustion ? Is water formed ? Why ? 

State the physical properties of carbon monoxid. Note the character 
of its flame. 

Experiment CI. — Pass a stream of carbon dioxid through a tube 
containing red-hot charcoal, and from this lead the gas through a 
bottle containing caustic soda. Collect the gas over water ; ignite 
a bottle of the gas. What is it ? 

This .experiment illustrates the method by which carbon 
monoxid is formed in coal stoves. The carbon dioxid 
formed by the combustion of the lower layers of coal passes 
through the hot coal above and is reduced to carbon mon- 
oxid, which burns with the characteristic blue name when 
it comes in contact with the air above the coal. 

286. Physical Properties. — Carbon monoxid is very spar- 
ingly soluble in water, and may be collected over water with 
very little loss. It may be liquefied, but with very great 
difficulty. It is very poisonous. When inhaled it combines 
with the haemoglobin, forming a bright red compound which 
cannot collect and distribute oxygen ; less than one per cent 



190 CHEMISTRY 

of carbon monoxid in the atmosphere gives rise to head- 
aches and giddiness, and if inhaled for any considerable 
time, insensibility and death quickly follow. The extremely 
poisonous nature of the " choke damp " resulting from a 
colliery explosion is due to the presence of carbon monoxid 
with the carbon dioxid formed as a product of the combus- 
tion. A pan of smouldering charcoal gives off this gas, and 
in certain countries is a frequent means of suicide. 

As carbon monoxid is odorless, coal gas could not be 
detected in the air were it not that carbon monoxid is 
usually accompanied by other gases having peculiar odors. 
Carbon monoxid is an important constituent of water gas. 
The chief objection to the use of water gas for the illumina- 
tion of dwellings arose from the fact that w T hile the water 
gas was more poisonous than the ordinary illuminating gas, 
it was odorless, and therefore leaks could not be detected 
except by the illness of persons. This objection has been 
overcome by adding to water gas certain gases which have 
partly an odor, and which increase the light. 

287. Chemical Properties. — At high temperatures carbon 
monoxid has a strong affinity for oxygen, and is an excel- 
lent reducing agent ; it forms an explosive mixture with air 
and with oxygen, which is the cause of the explosions which 
sometimes occur in coal stoves. 

288. Heat and Chemical Energy of the Combustion of 
Carbon. — The heat developed by the combustion of a 
gramme of carbon is about 8080 calories; something less 
than i as much as is developed by the combustion of an 
equal weight of hydrogen, but a larger amount than is 
developed by the combustion of any other element. 

It is an interesting fact that the two elements yielding 
the largest quantities of heat are the ones recovered from 



CARBON AND OXYGEN 



191 



the products of combustion by plants. We have here a 
species of endless chain; the fuel supply of the world 
can never be entirely exhausted. All fuels contain either 
carbon or hydrogen, and most of them contain both. 

289. Application of this Energy in doing Mechanical Work. 
— The steam engine is to-day our main reliance for power ; 
it may be considered as a machine which converts the 
chemical energy of fuel into heat, and the heat in turn 
into mechanical motion. The chemical energy of carbon 




is the principal source from which our power is derived, 
but it is not the only source; hydrogen forms some 20% 
of the weight of certain coals, and therefore supplies more 
than half of the heat units developed. The work done 
by explosives is derived directly from chemical energy 
without passing through the intermediate form. 

Experiment CII. To illustrate the transformation of the chemical 
energy into mechanical motion. — 1. Arrange apparatus as in sketch, 
the flask being empty. 

2. The bottle A is f full of water. 

3. Heat the flask with Bunsen burner. Why does water rise ? 
What chemical energy is used in this experiment ? In what other 
forms does it appear ? 

Experiment CIII. To illustrate the direct transformation of chemi- 
cal energy into mechanical motion. — 1. Remove the flask and tube 



192 CHEMISTRY 

leading to bottle A (Experiment 98). Close the hole in the rubber 
stopper. 

2. Refill the bottle and see that the tumbler is empty. 

3. Mix 3 grammes of sodium bicarbonate and an equal weight of 
tartaric acid. 

4. Raise the stopper of the bottle and pour the mixture into it. 
Describe and explain. 

The action is similar to that of the fire extinguisher, in 
which sulfuric acid is used instead of the tartaric acid used 
in this experiment. 

SECTION III.— A STUDY OF FLAME 

290. We have studied a number of cases of combustion, 
some of which developed flames, while others burned with- 
out flame. It will assist us to understand the cause of 
this difference in behavior, if we divide the combustible sub- 
stances which we have studied into two classes, (a) Those 
which burn with flame, such as hydrogen, water gas, sulfur, 
phosphorus, hydrogen sulfid, carbon monoxid, wood, rosin, 
kerosene, alcohol, paraffin, illuminating gas. (b) Those 
which burn without flame, as charcoal, iron, copper. Do 
all the gases mentioned above burn with flame ? All the 
liquids ? All the solids ? Are the substances which burn 
without a flame volatilized easily or with difficulty ? 

Experiment CIV. To examine the structure of the flame produced 
by the combustion of a hydrocarbon. — 1. Examine the flame of a 
candle, noting : (a) the blue cup-shaped portion, (b) the dark space, 
(c) the luminous cone, and (d) the thin layer. (To see the latter hold 
the candle near a blackboard. If this does not make it clear, hold 
flame in the sunlight and examine the shadow cast on white paper.) 

2. Make a sketch of the flame in your note-book, indicating the parts. 

Experiment CV. To determine which portion of the flame is 
hottest. — Lower a piece of cardboard into the candle flame until it 
nearly touches the wick; hold it in place until it begins to char on 
the upper side, then quickly remove it to prevent its taking fire. What 
portion of the flame is hottest ? Preserve this cardboard in your note- 



CARBON AND OXYGEN 193 

book. This shows a cross-section of the flame. To secure a longi- 
tudinal section hold a card horizontally, with one edge touching the 
wick below the flame ; revolve the card about the edge in contact 
with the wick until it is vertical. As soon as the side away from the 
flame begins to turn brown remove the card. Examine the section of 
the flame shown on the card. What portion of the flame is evidently 
hottest ? Coolest ? Is there any relation between the temperature 
and the intensity of the light of the various parts of the flame ? 

Experiment CVI. — 1. Spread the wick of the candle to make the 
flame as large as possible. 

2. Pass a match stick through the flame just above the wick, hold 
it there a few seconds, remove it, and quickly blow it out. 

3. Describe the charred portion of the match. Is the dark portion 
of the flame a zone of combustion ? 

Experiment CVII. Alternate. — 1. Thrust the head of a match into 
the dark portion of the candle flame. Hold it there while you count 
ten rapidly. Is it ignited while in the dark portion, or as it is with- 
drawn ? 

Experiment CVIIL To determine the state of the matter forming 
the dark portion of the flame. — 1. Hold a burning match stick two 
inches above the wick of a burning candle ; blow out the candle flame. 
What occurs when a stream of "smoke" which rises from the hot 
wick returns to a vertical position and comes into the match flame ? 
Is this " smoke " combustible ? 

2. Again extinguish the flame and hold a piece of filter paper in 
the stream of "smoke" ; after the smoke ceases examine the paper 
for evidence that the stream consisted of either solids or liquids. 

3. Relight the candle, hold a gas tube, drawn out to a point at one 
end, in the dark zone the pointed end upward ; hold a lighted match 
at the upper end. What is the state of the matter in the dark zone ? 
Explain how the paraffin reaches the flame ; also the changes of state 
which it undergoes. Is the candle flame due to the combustion of a 
solid, a liquid, or a gas ? 

Experiment CIX. To determine ivhy certain flames are luminous. — 
1. Adjust the supply of gas so that the Bunsen flame is non-luminous. 

2. Sprinkle a very little powered charcoal in the flame ; how is the 
amount of light affected ? 

3. Sprinkle reduced iron in the flame. 

4. Rub two pieces of charcoal together near the orifices at the base 



194 CHEMISTRY 

of the burner. How is the amount of light affected ? Explain how 
the charcoal reaches the flame. 

5. Make a spiral by winding a short piece of iron wire about a lead 
pencil ; hold this in the upper part of the flame ; how is the light 
affected ? How did the solids placed in the oxyhydrogen flame affect 
the amount of light ? 

6. Hold the mantle of a Welsbach burner in the flame. 

7. Close the holes at the base of the Bunsen burner ; note the 
changes in the amount of light. Hold a piece of glass tubing in the 
flame for a short time. Examine the tube for evidence that any 
element existed in the flame in a solid state. 

8. Open the holes in the base of the burner ; scrape some of the 
deposit from the glass tube, holding the tube near the openings at the 
base of the burner. How is the amount of light affected ? Explain. 
What is your opinion as to the cause of the light produced by burn- 
ing hydrocarbons ? 

Experiment CX. The Bunsen Burner. — 1. Examine the con- 
struction of a Bunsen burner. Make a sketch showing its parts. 

2. Describe the parts of a Bunsen burner flame. If necessary use 
the shadow. 

3. Explore the flame with a piece of platinum wire to determine in 
what zone or part of a zone the highest temperature is reached. 
(Judge by the degree of incandescence of the wire.) 

There is good authority for the statement that the lumi- 
nosity of certain flames is due to the presence of vapors of 
sufficient density to become incandescent at the tempera- 
ture of the flame, and it is probable that the luminosity of 
gas and candle flames is due to this cause acting conjointly 
with the presence of solid matter. 

291. Oxidizing and Reducing Flames. — In the outer portion 
of the candle flame and the Bunsen flame there is an excess 
of oxygen, hence substances heated in this portion of the 
flame are oxidized. In the inner portion of each of these 
flames there is a deficiency of oxygen, and substances con- 
taining oxygen are reduced when in this portion. The 
mouth blowpipe is usually used to increase the efficiency 



CARBON AND OXYGEN 



195 



of these flames. With a little practice one learns to close 
the opening between the mouth and nasal passages, and to 
force air through the 
blowpipe by contract- 
ing the cheek muscles, 
breathing regularly 
through the nose 
meanwhile. In this 
way one may blow a 
steady stream of air 
into a flame for sev- 
eral minutes. The Fig. 20. 
tip (5) of the outer 

flame is the most efficient oxidizing flame, and the tip (a) 
of the inner cone, the most efficient reducing flame. 




Experiment CXI. To reduce lead oxid. — 1. In a hollow made 
in a piece of charcoal place a small quantity of lead oxid, PbO. 

2. Using a blowpipe, heat it in the reducing flame until a metallic 
globule is obtained. 

3. Compare the physical properties of the globule with those of lead. 

Experiment CXII. To oxidize lead. — 1. Place a small piece of 
lead in a hollow made in a piece of charcoal. 

2. Heat the lead in the oxidizing flame. In what previous experi- 
ment was the coating formed on the charcoal obtained ? What is the 
substance ? 

REVIEW QUESTIONS 

1. Mention seven physical facts concerning carbon dioxid. 

2. What are carbonates ? How may they be detected ? 

3. Describe fully the formation of " fur " in the tea-kettle. 

4. What is the great supporter of vegetable life ? animal life ? 

5. What binary compounds are present in limestone ? How would 
you separate these binary compounds, and how would you cause them 
to combine again ? 

6. Describe an experiment in which chemical energy ultimately 
performs mechanical work. 



196 CHEMISTRY 

7. Compare the physical properties of carbon monoxid and carbon 
dioxid as follows: state, color, odor, and taste, solubility, weight, 
difficulty of liquefaction, and solidification, effect of pressure on solu- 
bility. Compare the chemical properties of carbon monoxid and car- 
bon dioxid as follows: combustibility, relation to animal life, to 
vegetable life, stability. 

8. Account for the unpleasant and sometimes dangerous explo- 
sions that frequently occur in coal stoves shortly after fuel is added. 

9. Carbon dioxid is nearly f oxygen, while air is only \ oxygen. 
Why is a flame extinguished in the former, and supported in the 
latter ? 

10. Compare the respiration of animals with that of plants. 

11. Show how haemoglobin and chlorophyll are of use to animals 
and plants respectively. 

12. Explain in detail the conditions of light and heat in the flame 
of a Bunsen lamp when the holes in the base of the lamp are (a) open, 
(b) closed. 

13. In household chemistry how is carbon monoxid formed ? 

14. State two reasons why organic substances are usually more 
suitable as fuels than inorganic substances. 

15. Are the life processes of animals essentially processes of oxida- 
tion or of reduction ? 

16. Is the process of assimilation by plants a process of oxidation, 
or reduction ? 

17. Why does not the air of cities become overcharged with carbon 
dioxid ? How is carbon dioxid absorbed at the poles ? in the winter ? 



CHAPTER XXVII 

HYDROCARBONS 

292. The binary compounds of hydrogen and carbon are 
known as hydrocarbons. Chemists are familiar with be- 
tween one and two hundred of them, and thousands more 
are theoretically possible. They all form oxids, hydroxids, 
etc., which are known as hydrocarbon derivatives, and which 
are so numerous that a list of their names would fill a 
good-sized volume. Fortunately, very simple relations exist 
between the chemical compositions and between the proper- 
ties of the members of several large groups or series ; and 
the study of these compounds is therefore greatly sim- 
plified. For example, the paraffin or the marsh gas series 
is based upon the compound CH 4 , and the first six members 
of the series have the following formula : — 

Methane, CH 4 , Butane, C 4 H 10 , 

Ethane, C 2 H 6 , Pentane, CsH^, 

Propane, C 3 H 8 , Hexane, C 6 H 14 . 

It will be seen that each formula differs from the pre- 
ceding by CH 2 and that each may be expressed by the 
general formula C n H 2n+2 . 

We shall study very briefly the three following sub- 



Methane, CH 4 , basis of the C n H 2B+2 series. 
Ethene, C 2 H 4 , basis of the C ?l H 2n series. 
Acetylene, C 2 H 2 , basis of the C 9l H 2n _ 2 series. 
197 



198 CHEMISTRY 

METHANE 
(MARSH GAS. FIRE DAMP) 

Formula CH 4 . — Molecular Weight 16 

293. Occurrence. — Marsh gas is found free in nature in 
large quantities. It is formed by the decay of vegetable 
matter in a limited supply of air. As the name indicates, 
it is found in marshes ; the bubbles which rise to the sur- 
face, when the mud at the bottom of the pond is disturbed, 
are largely marsh gas. It is one of the products of the 
process of reduction by which coal was formed, and exists, 
often under great pressure, in seams and crevices in the 
coal beds. Petroleum contains it; it often forms a large 
percentage of " natural gas " and is present in illuminating 
gas to the extent of 35 or 40 %. 

294. Preparation. 

Experiment CXIII. — 1. Mix 2 grammes of fused sodium acetate, 
NaC 2 H 3 2 , 4 grammes of caustic soda, and 5 grammes of quicklime. 
Reduce the mixture to a fine powder. 

2. Heat the mixture on a piece of sheet iron until all moisture is 
expelled. 

3. Charge a long ignition tube with the mixture, support it hori- 
zontally, and apply heat ; collect the evolved gas over water in small 
bottles. Note its physical properties. 

4. Thrust a lighted taper into a bottle of marsh gas. Describe the 
flame as to light and heat. What are the probable products of its 
combustion ? How can you prove that your answer is correct ? Test 
the bottle for carbon dioxid. Do you note any evidence of the forma- 
tion of water ? 

5. Determine whether the gas supports combustion. 

6. Determine whether it is heavier or lighter than air. 

Quicklime is used in this experiment to make the mass 
porous, and is not changed chemically. The reaction is as 
follows : — 

NaC 2 H 3 2 + NaOH = CH 4 + Na 2 C0 3 . 



HYDROCARBONS 



199 



QUESTIONS 

Why does this gas explode when mixed with the air and ignited ? 
In what proportion should the mixture explode with most violence ? 
Why do miners call this gas fire damp ? 

CH 4 + 2 2 = C0 2 + 2 H 2 0. 

If the above equation expresses the reaction which occurs when 
marsh gas explodes, how should the volume of the factors compare 
with that of the products (Avogadro's law) ? What effect should the 
heat developed by the combustion have upon the relative volumes ? 

Which of the products in the above reaction is known as choke 
damp and why is this name given it ? 

295. Uses. — Natural gas, which is largely marsh gas, is 
used extensively as fuel in various manufacturing establish- 
ments and in households. 

296. Marsh Gas in Coal Mines. — The violent explosions 
which frequently occur in coal mines are due to the ignition 
of an explosive mixture of fire damp and air. 

When fire damp explodes the products of its 
oxidation fill the mine; one of these products is 
known as choke damp. To prevent these explo- 
sions care is taken to thoroughly ventilate the 
mines, and miners' lamps (Fig. 21) are usually en- 
closed in wire gauze so that the flame cannot pass 
through the gauze and ignite the gas outside of 
the lamp. 

ETHENE 

(ETHYLENE. OLEFIANT GAS) 
Formula C 2 H 4 . — Molecular Weight 28 

297. Occurrence. — Ethene is one of the important con- 
stituents of illuminating gas, of which it forms from 
4 to 10%. 



200 CHEMISTRY 

298. Preparation. 

Experiment CXIV. (Performed by teacher. ) — In a large flask mix 
cautiously 80 cc. of sulfuric acid and 20 cc. of alcohol (C 2 H 6 0). 
Apply gentle beat and collect the gas evolved over water. Is the gas 
heavier or lighter than air ? Is it soluble in water ? Ignite a bottle 
of the gas and force the gas out by pouring water into the bottle. 
Describe the characteristics of the flame. What compounds are 
formed? From an inspection of the formulae, CH 4 and C 2 H 4 , would 
you expect the difference observed in the flames of marsh and olefiant 
gases ? Explain. 

The principal reaction which occurs in this experiment 
is expressed in the following equation : — 

C 2 H 6 = H 2 + C 2 H 4 . 
The strong affinity of sulfuric acid for water, withdraws 
hydrogen and oxygen from the alcohol in the proportion 
which they unite to form water. The gas thus prepared 
contains several impurities, which may be removed by pass- 
ing through strong sulfuric acid and then through sodium 
hydroxid. 

299. Properties. — Mixed with three volumes of oxygen 
and ignited, ethene explodes violently. Explain. It burns 
with a dull, smoky flame, when mixed with two volumes of 
chlorin and ignited, forming HC1 and C. Ethene may be 
liquefied at 0° C. by a pressure of 41 atmospheres. When 
the liquefied gas is rapidly evaporated, the extremely low 
temperature of — 140° C. may be obtained. Liquid ethene 
is therefore used in the liquefaction of oxygen and other 
gases requiring very low temperatures. 

ETHINE 

(ACETYLENE) 

Formula C 2 H 2 . — Molecular Weight 26 

300. Acetylene is formed when coal gas is burned in an 
insufficient supply of air. Its peculiar odor may be de- 



HYDROCARBONS 201 

tected when the flame of the Bunsen burner " snaps back " ; 
i.e. when the gas is ignited at the bottom of the burner. 

301. Preparation. 

Experiment CXV. — 1. Drop a small piece of calcium carbid, CaC 2 , 
into a tin cup that is about half full of water ; ignite the escaping gas. 
Describe its odor, flame. 

2. Hold a small piece of calcium carbid with tongs, drop a few 
drops of water on it, ignite ; then try to extinguish the flame with a 
miniature fire extinguisher made as in Experiment 99. 

Experiment CXYI. — 1. Place a small piece of calcium carbid, 
CaCo, under the mouth of a bottle arranged in the water pan for 
collecting a gas over water. 

2. Observe any change in the volume of the gas. Is it soluble in 
water ? What is its color ? 

3. Determine whether the gas is heavier or lighter than the air. 
Of the three hydrocarbons prepared, which produces the brightest 
light ? Does the brilliancy of the light produced depend upon the 
proportion of carbon in the compound ? Of the three, which requires 
the most oxygen for its complete combustion ? 

CaC 2 + 2 H 2 = CaH 2 2 + C 2 H 2 . 

302. Properties. — Acetylene is poisonous. It explodes 
violently under conditions which have not been well under- 
stood. At present, however, it seems to be established that 
the gas may be safely handled if the pressure under which 
it is confined does not much exceed one atmosphere. At a 
temperature of + 10° C. it is liquefied by a pressure of 63 
atmospheres. The deep red color obtained when acetylene 
is passed through a solution of cuprous chlorid in ammonia 
water is a very sensitive test for this gas. 

303. Derivatives. — Among the more important oxygen 
derivatives of the several homologous series of hydro- 
carbons are the hydroxids, the oxids, and the acids. The 
hydroxids are known as alcoJwls, and are formed by replac- 
ing one of the hydrogen atoms of some hydrocarbon with 



202 CHEMISTRY 

the radical, OH. The best known examples are methyl 
hydroxid, or wood alcohol, CH 3 OH, and ethyl hydroxid, 
or ordinary alcohol, C 2 H 5 OH. The alcohols have distinct 
basic properties, and combine readily with the various acids, 
forming ethereal salts. The oxids are known as ethers, the 
best known example being ordinary ether, or ethyl oxid 
(C 2 H 5 ) 2 0. The acids formed by the further oxidation of 
the hydrocarbons form an interesting group ; they combine 
with the inorganic bases, as well as with the alcohols, to 
form salts. In the following list the names and formulae of 
six members of the series of acids derived from the marsh 
gas series of hydrocarbons are given : — 



Formic acid, 


C-H9O2, 


or H.CO.OH. 


Acetic acid, 


C 2 H 4 2 , 


or CtL.CO.OH. 


Propionic acid, 


C 3 H 6 2 , 


or C 2 H 5 .CO.OH. 


Butyric acid, 


C 4 H 8 2 , 


or C 3 H 7 .CO.OH. 


Palmitic acid, 


ki&HffiQa 


or C 15 H 31 .CO.OH. 


Stearic acid, 


^18*1 36^2? 


or C 17 H 35 .CO.OH. 



These acids are commonly known as the fatty acids, be- 
cause they occur abundantly in most natural fats ; butyric 
acid is found in butter, palmitic acid in palm oil, and 
stearic acid in stearin. The so-called stearin candles are 
a mixture of palmitic and stearic acids. The fats, in a 
natural state, are ethereal salts formed by the union of the 
fatty acids with glycerin, a tribasic alcohol derived from 
propane, having the formula C 3 H 5 (OH) 3 . 

304. Soaps. — Like metallic salts, the ethereal salts are 
decomposed when treated with an alkaline hydroxid. The 
ethereal salts usually require a higher temperature to bring 
about the reaction, but all of them are decomposed when 
boiled with sodium or potassium hydroxid, the products of 



HYDROCARBONS 203 

the reaction being a salt of the alkalin base and an alcohol. 
As this sort of decomposition occurs in the process of making 
soap, it is called saponification. When a fat, as glycerin 
palmitate, for example, is boiled with sodium hydroxid, 
sodium palmitate (a soap) and glycerin are formed; the 
reaction may be expressed as follows : — 

C 3 H 5 (C 16 H 3 A) 3 + 3 KaOH = 3 NaC 16 H 31 2 + C 3 H 5 (OH) 3 . 

Ordinary soaps are usually palmitate or stearate of potas- 
sium or sodium. The sodium salts make hard soaps, and 
the potassium salts, soft soaps. The detergent or cleansing 
power of soap depends upon the fact that its solution either 
dissolves, or forms an emulsion of oily substances that water 
alone would have no effect upon. 

Experiment GXV1I. To make soap. — 1. Dissolve one part of 
sodium hydroxid in eight parts of water. 

2. Mix 50 cc. of the above solution with 50 cc. of castor oil and boil 
for half an hour. 

3. Add 200 cc. of water and bring to a boil. 

4. Add 20 grammes of common salt. The soap separates and 
solidifies as the liquid cools. 

REVIEW QUESTIONS 

1. Describe the artificial preparation of marsh gas, and state its 
properties, its use, and the manner of its occurrence in nature. 

2. Account for the presence of CH 4 in coal mines. Why is it 
dangerous ? What precautions should be taken to avoid this danger ? 

3. Distinguish between fire damp and choke damp, giving the 
chemical name, formula, and properties of each. 

4. Describe the preparation of acetylene, writing the reaction. 
State one important use of acetylene. 

5. Compare the physical properties of methane, ethene, and ethine ; 
the chemical properties. 

6. Describe the manufacture of soap ; write the reaction. 

7. What are soaps ? State the theory of the use of soaps in 
cleansing. 

8. Describe the manufacture of hard soap. 



CHAPTER XXVIII 
DESTRUCTIVE DISTILLATION 

305. Distillation. — The term distillation is applied to a 
number of operations which differ among themselves in 
many important respects, but in all of which a substance 
is heated and a vapor given off which is condensed in a 
cooled receiver. Two varieties of distillation depend only 
upon physical changes. The first variety, which might be 
called simple physical distillation, was illustrated by Experi- 
ment 43, in which water was separated from dissolved 
solids. The second variety is known as fractional distilla- 
tion, and is employed in separating liquids. If a mixture 
of water and ether be heated in a still, it begins to boil 
when slightly above the boiling point of ether, 35°, and the 
ether vapor accompanied by the small amount of water 
vapor, due to the normal evaporation of water at this tem- 
perature, is condensed. As the proportion of ether in the 
mixture is diminished the boiling point rises, and the pro- 
portion of water vapor condensed increases, so that it is 
customary to collect the distillate in separate portions or 
fractions of the whole, hence the name. By repeated dis- 
tillation of the "fractions" two or more liquids may be 
quite completely separated by this process. 

There are also two classes of distillation which involve 
chemical changes. The first of these was illustrated by 
Experiment 51, in which a chemical change was brought 
204 



DESTRUCTIVE DISTILLATION 205 

about by means of a reagent and the applied heat. As the 
temperature reached is sufficient to vaporize one of the 
products of the chemical change, it is easily separated from 
the other products by condensation. This is simple chemical 
distillation. 

In the remaining class, which is known as destructive or 
dry distillation, a chemical change is brought about by heat 
alone, the abseuce of reagents being an essential condition. 
In the many important applications of this process in the 
arts, the substance distilled consists of animal or vegetable 
matter; and when such substances are heated in a retort 
from which air is excluded, the products of their decompo- 
sition are quite different from the products of their com- 
bustion. Those products which are volatile may be 
separated by passing the vapors through a succession of 
condensers which are kept at different temperatures. 

The second method of preparing charcoal, the process of 
manufacturing coal gas, and process of preparing animal- 
charcoal or bone black are processes of destructive dis- 
tillation. Coal, petroleum, and natural gas were formed 
by the destructive distillation of organic matter under 
ground. 

306. Illuminating Gas. — There are two kinds of illumi- 
nating gas in common use, — coal gas, and the so-called water 
gas. Coal gas is generally prepared by the destructive dis- 
tillation of bituminous coal, although wood, resin, or petro- 
leum may be used. The coal is placed in fire-clay retorts 
which are heated by a coke fire. A vertical pipe connects 
each retort with a large horizontal pipe called the hydraulic 
main. When the coal is heated, the volatile products pass 
through the "riser" into the hydraulic main. Here the 
temperature of the gas is lowered somewhat by contact 



206 CHEMISTRY 

with the metal of the pipe, and some of the water vapor, 
tar, and ammonia salts are condensed. From the hydraulic 
main the gas flows through several hundred feet of pipe 
called the " condenser." The pipe is exposed to the air and 
is designed to cool the gas and condense the liquid prod- 
ucts of the distillation. Tar, benzol, tuluol, water, and am- 
monia salts are collected here ; and the mixture, called the 
ammoniacal liquor, is drawn off into cisterns. From the 
condenser the gas passes through a " scrubber," where it is 
washed. The scrubber is a large iron tank, frequently six 
or eight feet in diameter and twenty feet high, filled with 
coke, blocks of wood, or scraps of tin, the object being to 
expose a large surface to the gas. A spray of water is 
introduced at the top of the scrubber, and the material 
filling it is thus kept moist. The remainder of the tar 
and ammonia salts are here removed, and the gas passes on 
to the purifier. This is a large rectangular box, frequently 
twenty feet square and four feet deep, and is filled with 
layers of quicklime which absorbs water, carbon dioxid, 
and hydrogen sulfid. The gas passes through successive 
purifiers until a test shows that all the above substances 
have been removed. It then passes to the gas holders and 
is ready for the consumers. Of the products of distillation 
of bituminous coal, one is solid, viz. coke, which is found in 
the retort; four are liquid, viz. tar, benzol, tuluol, and water 
containing a variety of ammonia salts in solution; eight 
are gases, viz. hydrogen, nitrogen, marsh gas, olefiant gas, 
acetylene, carbon monoxid, carbon dioxid, and hydrogen 
sulfid. It seems likely that a small amount of the vapors 
of benzol and tuluol are also present in the gas and that 
they increase the illuminating power. The gas delivered 
to the consumer is a mixture of all the above gases except 
hydrogen sulfid and carbon dioxid. 



DESTRUCTIVE DISTILLATION 207 

Experiment C XVIII. (For two students. ) To prepare coal gas. — 
1. Fill a gas-pipe retort* 6 inches long, one-fourth full of pieces of dry 
pine wood ; support it so that it may be strongly heated. 

2. Connect two bottles so that the gas evolved shall bubble through 
the liquids which they contaiu. 

3. The first bottle should be two-thirds full of cold water, the 
second one-third full of lime-water. From the second bottle lead the 
gas to the water pan, collect two bottles of the pure gas ; then substi- 
tute a tube drawn out to a point for the delivery tube in the water pan 
and ignite the gas. Describe the flame. When the flow of gas ceases, 
examine the bottle of lime-water. Of what two substances do you find 
chemical evidence here ? Examine the first bottle for evidences of 
ammonia, tar, and oil. Open the retort and examine the coke. 

Experiment CXIX. Examination of Illuminating Gas. — 1. Hold a 
strip of filter paper moistened with a solution of lead acetate, in 
a stream of gas coming from the Bunsen burner. (See Art. 170.) 
What substance is detected by this test? 

2. Hold a strip of moistened red litmus paper in a stream of the 
gas. The presence or absence of what impurity is indicated by this 
test? 

3. Pass a stream of the gas through a bottle of lime-water. What 
impurities have you found in the gas tested ? What is your conclusion 
concerning the efficiency of the purifiers at the gas works furnishing 
the gas tested ? 

307. Coke. — Large quantities of coke are now made 
from the fine coal or slack which was formerly considered 
valueless and which accumulated rapidly about coal mines. 
Bituminous coal, containing between 20% and 30% of 
volatile hydrocarbons, melts when burned or when heated 
in a retort, and on cooling leaves a hard porous mass 
having a metallic lustre. The slack is thoroughly washed 

* Obtain of the plumber a f inch nipple 6 inches long, a f cap, a f 
to £ reducer, and a piece of \ inch pipe 6 inches long. Put them 
together as shown in the cut. 



208 CHEMISTRY 

and placed in ovens somewhat the shape of a beehive, a 
limited supply of air is admitted on top of the slack, the 
heat of the oven ignites it, and the combustion is continued 
as long as smoke is evolved. When this ceases, the air 
supply is cut off and the oven allowed to cool for about 
twelve hours ; the coke is then quenched with water. Coke 
thus prepared is superior to all other fuels for iron smelting ; 
while it does not burn as rapidly as charcoal, and therefore 
does not produce quite as high a temperature, it is able to 
resist the pressure caused by the weight of ore and flux 
in the highest furnaces. Charcoal can only be used in the 
smaller furnaces, because it is crushed by the great weight 
above it. Anthracite, on the other hand, is able to with- 
stand the mechanical effects, but it burns so slowly that it 
does not produce the required temperature. Coke, there- 
fore, combines the good qualities of both charcoal and 
anthracite; it yields the required temperature and is able 
to withstand the charge in the highest furnaces. 

For domestic purposes, coke is an economical fuel, and 
possesses the further advantage of being smokeless, but is 
under the disadvantage that when the temperature of the 
combustion falls off to any considerable extent, the carbon 
clioxid produced may be delivered into the living rooms 
instead of being carried off by the chimney. 

308. Coal. — Examination of the various varieties of coal 
shows that they represent various stages in the natural 
destructive distillation of vegetable refuse. When a mass 
of such refuse is covered with a layer of clay or mud so as 
to exclude the air, and is subjected to pressure due to the 
accumulation of rock above it, or to heat from beneath it, 
a complex molecule of cellulose, C^H^O^ (woody fibre), is 
broken up just as it is in a retort, the composition of the 



DESTRUCTIVE DISTILLATION 209 

residue depending upon the degree of heat and the amount 
of pressure to which the deposit has been subjected. Ac- 
cording to one theory, petroleum and natural gas are the 
liquid and gaseous products of the distillation. The objec- 
tion to this theory is that the occurrence of petroleum seems 
to have no necessary connection with the occurrence below 
of coal seams. The most probable theory seems to be that 
both petroleum and coal are formed from organic matter, 
but of different conditions, and that natural gas is derived 
chiefly from the slow distillation of petroleum. That each 
of these substances has been formed by the destruction 
of organic matter may be regarded as certain. These 
processes have been in progress through long geological 
eras, and the coal of the older formations is more com- 
pletely transformed than that of the recent formations. 
Anthracite or hard coal corresponds to the coke left in 
the gas retort, and is nearly pure carbon. It occurs only 
in the older geological formations, and in these formations 
only in locations showing that the region has been up- 
turned, thus subjecting the coal to high temperature and 
great pressure. Anthracite burns without flame or smoke, 
and ignites with difficulty. 

Bituminous or soft coal also occurs in the older geologi- 
cal formation, but the evidences of high temperature and 
great pressure are always lacking 5 it is softer than anthra- 
cite, and burns with a smoky flame. Lignite, or brown coal, 
occurs in more recent geological formation, and often retains 
the structure of the wood from which it was formed. 

Peat is an open mass of vegetable refuse of recent forma- 
tion. The following table, showing the compositions of 
these substances, will give the student an idea of the nature 
of the changes which the various kinds of coal have under- 
gone : — 



210 



CHEMISTRY 





C 


II 





Wood 


49.7% 
59.5 


6.2% 


43 % 


Peat 


5.5 


33 


Brown Coal 


68.7 


5.5 


25 


Bituminous Coal 


81.2 


5.5 


12.5 


Anthracite Coal 


95 


2.5 


2.5 



309. Ammonia from Compost Heaps. — When marsh gas 
is formed in nature it is a product of decay ; the molecules 
of the decomposing substance breaking up into simpler mole- 
cules. Animal substances usually contain carbon, hydro- 
gen, nitrogen, and oxygen. When they decay in a limited 
supply of air, the oxygen combines with the carbon and 
hydrogen, and if there is not enough to oxidize all of these 
elements, some of the carbon is given off, combined with 
hydrogen, as marsh gas. The nitrogen also combines with 
hydrogen as ammonia gas (NH 3 ). These two substances 
may be regarded as intermediate products in the process of 
decay. Some animal substances give off ammonia when 
they decompose in air, but many others yield it when the 
process is carried on in a limited supply of air. 

REVIEW QUESTIONS 

1. Describe the process of destructive distillation as employed on 
an extensive scale in the industrial arts. State reasons for employing 
this process. 

2. Describe the preparation of coke, and state for what and why- 
it is used. 

3. Discuss petroleum as to (a) origin, (&) method by which 
obtained, (c) products. 

4. State the theory of the formation of (a) coal, (&) petroleum, 
(c) natural gas. 

5. Describe the process of destructive distillation as accomplished 
by nature on an extensive scale. 

6. Account for the formation of ammonia in compost heaps. 

7. Should destructive distillation be considered a process of oxida- 
tion or of reduction ? 



CHAPTER XXIX 
FERMENTATION 

310. Definition. — As suggested by its derivation, from 
"fervere " (to boil), this term was originally applied to all 
chemical changes involving the effervescence of a liquid. 
In its modern acceptance, however, it has nothing at all to 
do with effervescence, being used to designate a peculiar 
class of decompositions which is produced in complex 
organic substances by certain living organisms, or by 
chemical compounds formed by these organisms. The most 
familiar illustrations of fermentation are the fermentation 
of fruit juices, or fruits, the souring of cider, the decay of 
vegetable matter, the putrefaction of nitrogenous matter, 
the souring of milk, and that which occurs in the process of 
making bread. 

Fermentation occurs more rapidly in the presence of 
moisture than in dry substances, and the process is more 
active at temperatures between 25° and 35° C. than at either 
higher or lower temperatures. 

Most organic substances are subject to fermentation, 
although those of simple molecular structure are less sub- 
ject to it than the complex molecules, and a few of these 
like cresol, phenol, or creosote are valuable agents for the 
prevention of fermentation. The chemical changes consist 
in the breaking down of complex molecules, forming simpler 
groups of atoms, either by the absorption of the hydrogen 
and oxygen of water, or by slow oxidation: but in some 
211 



212 CHEMISTRY 

cases it consists in a rearrangement of the atoms in the 
molecule, forming an isomeric compound. 

The changes cannot be induced by any means except the 
presence of ferments, and each ferment produces its special 
change, which is often the precise opposite of that which 
the chemical properties of the elements forming the mole- 
cule which is decomposed would lead us to expect. 

311. Ferments. — Most ferments are microscopic plants 
of very simple structure, which multiply with great rapid- 
ity ; they derive the material needed for their growth from 
the medium in which they are placed, transforming it into 
other substances. They are variously known as germs, 
microbes, bacteria, etc. 

Yeast, the most familiar of these ferments, is a micro- 
scopic plant found in the air and about certain fruit trees. 
The yeast of the store is grown on some suitable culture 
medium, as the potato or corn meal. 

Besides these organized ferments which cause fermenta- 
tion as a result of their peculiar life processes, there is a 
group of chemical, or unorganized ferments, known as 
enzymes, of which diastase, pepsin, and ptyalin are exam- 
ples. Although the enzymes are not living organisms, they 
are all derived directly from animal or vegetable life. The 
chemical action caused by the enzymes is not well under- 
stood ; the decompositions are less complete than those due 
to organized ferments, and usually consist simply of a 
rearrangement of the atoms of the molecule. Like organ- 
ized ferments they are most active at certain temperatures, 
which vary for the different ferments. Their characteristic 
properties are destroyed when their aqueous solution is 
heated to the boiling point, but in a dry state they can 
withstand a much higher temperature; pepsin, for example, 



FERMENTATION 213 

may be heated to 170° C. without losing its ability to cause 
fermentation. There is some doubt as to whether the real 
cause of fermentation is the microscopic organism, to which 
the action is usually attributed, or a chemical compound 
excreted by the organism. 

312. Alcoholic Fermentation. — The fermentation induced 
by yeast converts sweet fruit juices and solutions contain- 
ing a sugar known as glucose, C^H^Oq, into ethyl alcohol, 
C 2 H 6 ; carbon dioxid is liberated, and one or two other 
substances are formed, but the principal reaction is : — 

C 6 H^0 6 = 2C 2 H 6 0+2C0 2 . 

Several microorganisms besides yeast induce alcoholic 
fermentation, and they are so abundant that all fruit juices 
seem to ferment spontaneously; the ferment, however, is 
either obtained from the air or was clinging to the outside 
of the fruit. The fermented liquors which are obtained 
vary as widely in their properties as do the fruits from 
which they are made, and are known by different names. 
Hard cider is fermented apple juice, wine is fermented 
grape juice, perry is fermented pear juice. 

The percentage of alcohol in wine varies considerably ; if the fer- 
mentation is checked before all of the sugar has been converted into 
alcohol, a sweet wine is obtained which will contain less alcohol than 
it would have contained if the fermentation had been allowed to pro- 
ceed ; besides this, the amount of sugar which may be converted into 
alcohol is greater in some grapes than in others. Perhaps the average 
amount of alcohol in wine is between 15 and 20 %. 

Alcoholic fermentation occurs only in a dilute solution of 
some sugar, but certain of the several ferments which in- 
duce it can convert other substances into a sugar ; for this 
reason alcoholic fermentation often occurs in substances 
containing starch, but it is always preceded by a reaction 



214 CHEMISTRY 

which converts the starch into sugar. In the process of 
brewing ale and beer the first step is to convert the barley 
into malt ; the maltose, a sugar found in the malt, is then 
extracted, to this yeast is added, and the fermentation 
which ensues yields a liquid containing between 3 and 9 % 
of alcohol. In the manufacture of whiskey, the Indian corn, 
rye, or other grain undergoes a similar change before alco- 
holic fermentation takes place. This is also true of the 
flour in the process of bread making. 

Experiment CXX. A Study of Alcoholic Fermentation. — 1. Dis- 
solve about a tea.spoonful of glucose in 100 cc. of water in a flask, add 
a small piece of yeast, and arrange a delivery tube so that any gas 
which may be evolved shall bubble through lime-water. 

2. Set the apparatus in a warm place for twenty-four hours. 

3. Examine the lime-water for evidence that carbon dioxid has 
been evolved. 

4. Arrange a test tube in a bottle of cold water in such manner 
that it may serve as a condenser, heat the flask very gradually, receiv- 
ing the vapor in the test tube. 

5. Examine the first few drops condensed, noting odor, combusti- 
bility, etc. 

313. Bread Making. 

Alcoholic fermentation plays an important part in mak- 
ing bread, but the changes which occur in the oven are not 
less interesting. Taken together these two processes con- 
vert the comparatively indigestible flour into one of our 
most wholesome foods. It is worth our while to consider 
briefly the various steps in the process, with the objects to 
be attained in each. 

(a) The Mixing. 

Flour, salt, yeast, and milk or water are mixed into 
dough. In this process the starch granules are to be 
thoroughly moistened, and the yeast evenly distributed 
through the mass. The latter object may be best accom- 



FERMENTATION 215 

plished by vigorously beating with, a spoon, when enough of 
the flour has been added to give the mixture the consistency 
of a rather thick batter ; much oxygen from the air is at 
the same time distributed through the mass. After ten or 
fifteen minutes' beating the remainder of the flour is worked 
in, and the dough set in a warm place (75° F.) to rise. It 
is desirable that all of the flour required be added at this 
time, as the flour is rendered more digestible, and acquires 
a better flavor from fermentation. 

The addition of a little sugar renders the fermentation 
more rapid. The use of milk instead of a part of the 
water is strongly recommended, as it materially increases 
the value of the bread as a food. 

(5) TJie Fermentation. 

In this process, which lasts about three hours under 
proper conditions, some of the starch is changed to sugar, 
and then to alcohol and carbon dioxid ; the gluten is modi- 
fied and perhaps combined with the starch granules, and 
the albumen is rendered insoluble. The escape of the 
gases is hindered by the hydrated gluten, which is elastic, 
and as the gases form, the mass increases in bulk and 
becomes porous. If the fermentation continues too long, 
acetic fermentation sets in, and the mass becomes sour. 

(c) The Baking. 

As the temperature of the dough rises, the starch granules 
burst, the yeast is killed and fermentation ceases, the gases 
are expanded, increasing the porosity of the dough, some of 
the water together with a portion of the carbon dioxid and 
of the alcohol are expelled, the albumen is coagulated and 
rendered more digestible, some of the starch is changed 
into dextrin, some caramel is formed in the crust, and a 
distinct flavor is developed. 



216 CHEMISTRY 

314. The Formation of Acids by Fermentation. — In all 

alcoholic fermentation, including the fermentations which 
form other kinds of alcohol than that produced by yeast, 
the molecule of the substance acted upon takes hydrogen 
and oxygen, and all of the alcohols formed have basic 
properties. We now consider a kind of fermentation which 
yields an acid product. Familiar examples of this kind of 
fermentation are the souring of milk and the souring of 
cider or wine. 

315. Acetous Fermentation. — This kind of fermentation 
is due to the action of a ferment commonly known as 
vinegar plant, or as "mother of vinegar." It is a micro- 
organism, and in no way related to the so-called vinegar 
eels which are sometimes seen in vinegar. The acetous 
ferment attacks alcoholic liquids, and changes the alcohol 
which they contain into acetic acid, with the following 
reaction : — 

C 2 H 6 + 20 = C 2 HA + H 2 0. 

It should be noted that this is a process of oxidation. 
If acetic fermentation is not checked, the acetic acid 
formed is oxidized to carbon dioxid and water. 

316. Vinegar is a liquid containing from 2 to 4 % of 
acetic acid. It is ordinarily prepared by introducing the 
acetous ferment into cider, wine, or other liquid containing 
a small per cent of alcohol. The process proceeds very 
slowly. The so-called mother of vinegar, which is com- 
monly used to start acetous fermentation in a fresh cask 
of the liquid to be fermented, is a mass of minute plants 
which is found in most samples of vinegar. 

317. Putrefaction and Decay. — The term putrefaction is 
employed to denote a process of fermentation developed in 



FERMENTATION 217 

nitrogenous organic substances by microorganisms, which is 
accompanied by the evolution of foul odors. 

This action is entirely distinct from the decomposition 
due to the action of oxygen, although under ordinary con- 
ditions these two processes occur simultaneously. 

The decay of wood and other vegetable tissue, and the 
destruction of textile fabrics by mildew, are due to the 
action of microorganisms, which require both oxygen and 
moisture in their life processes ; for this reason these 
varieties of fermentation do not occur in perfectly dry 
substances, nor in those which are immersed in water. 

318. Methods of Preventing Fermentation. — Various meth- 
ods of preventing the decay of organic matter used for food 
are in common use. In all of them the growth of the 
ferment organisms is prevented, either by bringing about 
conditions unfavorable to such growth, or by the use of 
chemical agents which destroy or retard the growth of 
the organisms. The following methods may be mentioned 
by way of illustration ; — 

1. Drying. — Ferments cannot grow without water ; hence 
dried fruit, dried meats, and condensed milk keep much 
longer than when in their normal condition. 

2. Cold Storage. — The efficiency of cold storage depends 
upon the fact that most ferments are inactive at low tem- 
i:>eratures. 

3. Canning. — In the process of canning meats, fruits, 
and vegetables, the material is raised to a high temperature 
(not necessarily to the boiling point), to destroy all ferments, 
and the cans are sealed while the material is still hot. 

4. By the Use of Alcohol or Vinegar. — In certain kinds of 
fermentation the action diminishes in vigor as the product 
of the chemical action increases, and finally ceases when a 



218 CHEMISTRY 

definite percentage of the product has accumulated. It 
thus appears that the product of the fermentation has an 
inhibitory effect upon the chemical action, if, indeed, it is 
not poisonous to the ferment organism. This is the case in 
both alcoholic and acetous fermentation ; hence the use of 
alcohol as a preservative agent in brandied fruits, and vine- 
gar in pickles. 

5. Preserving and Spicing. — Spices and heavy syrups 
prevent the growth of ferments, and fruits are often pre- 
served, even when exposed to the air, by covering them 
with syrups or strong infusions of spices. 

6. By the Use of Antiseptics. — Among the chemical agents 
employed as antiseptics are : common salt, used in curing 
meats and fish ; and wood smoke, which is used to preserve 
hams, tongue, fish, etc., because of the creosote which it 
contains. Salicylic and boracic acids have also been used 
to some extent in preserving meat and fruits, but the pro- 
priety of such use is at least questionable, as it is a well- 
known fact that even in comparatively small doses they 
interfere with digestion. 

The decay of wood is materially lessened by impregnating 
it with some antiseptic, such as carbolic acid or creosote, 
and mildew in canvas is prevented by saturating the fibres 
of the cloth with zinc carbonate, lead sulfate, or some simi- 
lar substance. 

REVIEW QUESTIONS 

1. What is yeast ? For what is it used ? Explain the chemical 
action involved in this use. 

2. Define fermentation. What substances are subject to fermen- 
tation ? What is the general character of the chemical changes pro- 
duced ? 

3. Describe the process of making bread. What is the object of 
the fermentation ? What chemical changes occur in the oven ? 



FERMENTATION 219 

4. Discuss the acetous fermentation. What is vinegar ? How is 
it prepared ? 

5. "Why does milk sour ? 

6. Mention eight ways in which the decay of fruits may be pre- 
vented. 

7. In what four ways may meats be preserved ? 

8. Mention five processes based upon alcoholic fermentation. 



CHAPTER XXX 
PHOSPHORUS 

Symbol P. — Atomic Weight 31 

319. Occurrence. — In combination with oxygen and 
metals, phosphorus is widely distributed in nature. 
Calcium phosphate is present in all fertile soils, and has 
been shown to be necessary to the growth of plants ; it 
forms about 60 % of the bones of animals. In the mineral 
kingdom several phosphates occur. 

320. Preparation. — Phosphorus is prepared by treating 
calcined bones with sulfuric acid. The following reaction 
occurs : — 

Ca 3 (P0 4 ) 2 + 3 H 2 S0 4 = 3 CaS0 4 + 2 H 3 P0 4 . 

The calcium sulfate is insoluble in water, and is separated 
from the solution of orthophosphoric acid by filtration ; the 
solution is concentrated, mixed with carbon, and distilled 
in bottle-shaped clay retorts. When the retort reaches a 
white heat, the phosphorus distills over, and is condensed 
under water. The crude phosphorus thus obtained is re- 
fined by processes which are carefully guarded as trade 
secrets. 

321. Physical Properties. — When freshly prepared, phos- 
phorus is a colorless, transparent, wax-like solid which 
gradually becomes coated with a film which is at first 
white, then yellow, brown, red, and finally black. At 

220 



PHOSPHORUS 221 

0° C. it is brittle, but at ordinary temperatures it is flexible ; 
it melts at 44°, and boils at 290°. It is insoluble in water, 
but dissolves readily in carbon disulfid, and less freely in 
chloroform, alcohol, petroleum, and other solvents. When 
a solution of phosphorus in carbon disulfid is evaporated, 
the phosphorus is left in exceedingly minute particles, and 
if the evaporation takes place on a non-conductor of heat, 
the oxidation will raise the phosphorus to its kindling tem- 
perature, and cause it to burst into flame. 

Experiment CXXI. — 1. Pour 2 or 3 cc. of a solution of phos- 
phorus in carbon disulfid on a piece of filter paper. 

2. Place the paper on the base of your retort stand, and observe 
any changes that occur. Do you note the formation of crystals of 
phosphorus ? Are white fumes evolved ? 

3. After the burning has ceased, examine the paper. Is it entirely 
consumed ? Do you discover a coating on portions of the paper 
which might have prevented its burning ? On which portions is it 
thickest ? From what source might such a coating have been derived ? 

322. Chemical Properties. — Phosphorus belongs to the 
nitrogen family, but its chemical activity is in sharp con- 
trast with that of nitrogen. It is one of the most active 
elements. 

When exposed to the air phosphorus is slowly oxidized 
and gives off fumes which are faintly luminous and visible 
in a dark room ; if its temperature is slightly increased, 
as by the heat of the hand or by friction, it bursts into 
flame ; for this reason phosphorus is always kept under 
water, and should also be cut only under water. Its 
kindling temperature is 60°, and its specific gravity 1.82. 

The name phosphorus is derived from the Greek, and 
means light bearing. The mark left by a match on any 
surface in a dark room is phosphorescent. The affinities 
of phosphorus for oxygen and for iodin have been illus- 



222 CHEMISTRY 

trated. It has also strong affinity for sulfur and for the 
halogens, and it combines directly with the metals, formiug 
phosphids. 

Phosphorus is a powerful poison ; in large doses it causes 
death in a short time, and in smaller doses produces intense 
pains in the stomach, and usually brings on convulsions. 

323. Red Phosphorus. — This important allotropic modi- 
fication of phosphorus may be formed by subjecting the 
ordinary variety to the action of light, heat, or electricity. 
In the arts it is prepared by heating ordinary phosphorus 
in cast iron retorts, from which air is excluded, to between 
240° and 250° C, by means of a bath of melted solder. 
If the temperature rises to 300°, the red phosphorus is 
changed back to the ordinary variety. After fifty or sixty 
hours of heating at 240°, there is found in the retort a layer 
of hard lumps of red phosphorus containing a small per- 
centage of the ordinary variety. To remove this, the 
material is ground to a powder under water, and treated 
with a solution of caustic soda, or with carbon disulfid, 
either of which dissolves the ordinary phosphorus. 

If one part of iodin be added to 100 parts of the ordi- 
nary or vitreous phosphorus, and the mixture is heated, 
the change to red phosphorus occurs below 200° C. 

324. Properties of Red Phosphorus. — Red phosphorus is 
a chocolate-red, amorphous powder; it is odorless, opaque, 
and insoluble in the solvents of the ordinary variety; it 
is not poisonous. 

In dry air, at ordinary temperatures, there is practically 
no oxidation, and therefore no phosphorescence, but in 
the presence of moisture it is very slowly oxidized. 

The melting point of red phosphorus is evidently above 
the temperature at which it changes back to the ordinary 



PHOSPHORUS 223 

variety, for it lias never been melted. It is somewhat 
heavier than ordinary phosphorus ; specific gravity, 2.25. 
Active combustion begins in air at 300°, the product of the 
combustion being identical with that of the ordinary variety. 

325. Uses of Phosphorus. — The principal use of phos- 
phorus is in the manufacture of matches, although small 
amounts are used annually in poisons for rats and vermin. 
Its compounds, the phosphates, are used as fertilizers, and 
certain other compounds are used in medicine and in the 
laboratory. 

Matches. — The process of manufacturing the common 
sulfur match was described in § 161; the disagreeable 
odor of such matches is obviated if paraffin or stearin is 
used instead of sulfur, and matches prepared in this way 
are often called "parlor matches." The following is one 
of the many recipes for a paste with which to tip parlor 
matches : — 

Vitreous phosphorus 6.4 parts 

Lead dioxid 50 " 

Dextrin 30.6 " 

Water 13 " 

100 " 

Most parlor matches made in this country contain potas- 
sium chlorate instead of lead dioxid as the oxidizing agent ; 
such matches snap and burn with great vigor, but the heads 
sometimes fly off, inflicting severe burns or causing fires. 

Various attempts have been made since the discovery 
of red phosphorus to prepare a non-poisonous match; the 
efforts were comparative failures except the safety match. 
These matches do not contain phosphorus, but some makers 
put other poisons in the paste. The Swedish safety matches 



224 CHEMISTRY 

are tipped with a paste made of antimony sulfid, potassium 
chlorate, and glue ; they are ignited by rubbing them upon 
the side of the box, which is coated with a paste made 
of red phosphorus, antimony sulfid, and glue. In several 
European countries the use of any other kind of match 
is prohibited by law. 

The paste with which all matches are tipped consists of one or 
more oxidizable substances mixed with compounds which can supply- 
oxygen. 

In the common match one of the oxidizable substances is phos- 
phorus, which requires but little friction to ignite it. When the oxi- 
dizing agent is potassium chlorate, the phosphorus is oxidized, and 
potassium chlorid remains. 

In the safety match, the match head contains antimony sulfid as 
the oxidizable substance and an oxidizing agent, while the rubbing 
surface contains no oxidizing agent ; this lack of oxygen prevents the 
combustion of the rubbing surface when the match is struck. 

The only difference between the chemical actions in the heads of 
the common and the safety match is, that in the former, phosphorus 
is oxidized, and in the latter, antimony sulfid is oxidized. 

326. Oxids of Phosphorus. — Like nitrogen, phosphorus 
forms several compounds with oxygen ; the best known of 
them are the trioxid, P 4 6 , and the pentoxid, P 2 5 . 

327. Phosphorus Trioxid, P 4 0„, is a white crystalline solid 
formed by the slow combustion of phosphorus in a limited 
supply of air. It is slowly dissolved by cold water, forming 
phosphorous acid, H 3 P0 3 . In hot water violent action occurs 
in which the spontaneously inflammable hydrogen phosphid, 
PH 3 , is evolved and red phosphorus is formed. 

328. Phosphorus Pentoxid, P L ,0,-, is a snow-white amor- 
phous, odorless, very voluminous powder. It is the chief 
product formed when phosphorus burns in air or in ox} r gen, 
and was formed in Experiments 30, 56, and 57. It is very 
deliquescent, dissolving in the water absorbed if exposed to 



PHOSPHORUS 225 

moist air for a short time, it must therefore be kept in glass 
tubes closed at both ends. When thrown into water it dis- 
solves with a hiss, forming metaphosphoric acid. Its affinity 
for water is its most important property and makes it our 
most useful desiccating agent.- The same property enables 
it to decompose nitric acid as follows : — 

2M0 3 -H 2 = N 2 5 , 

and to abstract water from many compounds containing 
carbon, hydrogen, and oxygen, thus converting them into 
hydrocarbons. 

329. The Phosphorus Oxyacids. — Phosphorus combines 
with hydrogen and oxygen to form several acids. Three 
of the more common are 

Hypoxmosphorous acid, H 3 P0 2 
Phosphorous acid, H 3 P0 3 

Phosphoric acid, H 3 P0 4 

Hypophospliorous acid is monobasic and is chiefly im- 
portant because of the value of its salts in medicine. 

Phosphorous acid is dibasic and is of little importance 
save from a theoretical standpoint. 

Phosphoric acid is the most important of the acids ; its 
salts are the principal compounds of phosphorus. 

Phosphorus pentoxid combines with water to form three 
distinct acids : Metaphosphoric Acid, HP0 3 , formed when 
the pentoxid dissolves in cold water — 

P 2 5 + H 2 = 2HP0 3 ; 

Orthophosphoric Acid, H 3 P0 4 , formed when the pentoxid 
dissolves in boiling water, — 

P 2 5 + 3H 2 = 2H 3 P0 4 ; 



226 CHEMISTRY 

and Pyrophosphoric Acid, H^P.O^, which is not formed by 
direct combination. 

Orthophosphoric acid may be converted into either of the 
others by the application of heat. At 213° it is converted 
into pyrophosphoric acid with the following reaction : — 

2 H 3 P0 4 = H 4 P 2 7 + H 2 0. 

At 400° metaphosphoric acid is formed. 

H 4 P 2 7 = 2HP0 3 + H 2 0. 

Metaphosphoric acid is monobasic, orthophosphoric acid is 
tribasic, and pyrophosphoric acid is tetrabasic; from these 
three acids, therefore, eight different salts, phosphates of a 
univalent metal, may be formed. 

330. Phosphoric Acid, H 3 P0 4 , or orthophosphoric acid, as 
it is sometimes called, may be prepared in several ways 
besides that described in the last article ; as, for example, 
by oxidizing phosphorus with nitric acid, or by decom- 
posing bone-ash, Ca 3 (P0 4 ) 2 , with sulfuric acid, as in the 
preparation of phosphorus. The solution thus obtained is 
evaporated to a thick syrup, from which hard, colorless, 
prismatic crystals, which are very deliquescent, may be 
obtained. 

As phosphoric acid is tribasic, it forms three series of 
salts; thus the metal sodium forms the following phos- 
phates : — 

Trisodium phosphate, Na 3 P0 4 

Hydrogen disodium phosphate, H]Sra 2 P0 4 
Dihydrogen sodium phosphate, H 2 NaP0 4 

The first of these is the normal phosphate, and the others 
are called acid phosphates. AVe have here, as we had in 
the case of the acid sodium carbonate, an acid salt which 



PHOSPHORUS 227 

gives an alkaline reaction with litmus paper. For this 
reason there is some objection to the classification of salts 
as acid and normal, and the suggestion that they be called 
primary, secondary, tertiary, etc., depending upon the num- 
ber of atoms of a metal which the molecule contains, has 
been somewhat favorably received. The common sodium 
phosphate is the second of the three mentioned above. 

There are several important double phosphates formed by 
replacing part of the hydrogen of the acid with one metal 
and the rest with another, ammonium magnesium phos- 
phate, NH 4 MgP0 4 ; and hydrogen sodium ammonium phos- 
phate, ffiSTaNK^PO^ commonly called microcosmic salt, are 
examples of the double salts. 

331. Allotropism. — Phosphorus presents one of the best 
illustrations of allotropism, not only because of the differ- 
ence in the physical and chemical properties of the varieties, 
but also because of the ease with which either variety may 
be converted into the other. In addition to the two modifi- 
cations of phosphorus already described, a metallic form is 
known, but it is rare and of little use. 

Allotropism is similar to polymerism, defined in § 337, 
but the term is usually applied to elements instead of com- 
pounds. Some writers, however, apply the term to those 
compounds existing in two forms, which differ only in their 
physical properties. 

It is probable that as our knowledge increases we shall 
be able to prove that all cases of allotropism are due to 
differences in the number of atoms in the molecule of the 
element. In the case of ozone, which is an allotropic 
modification of oxygen, this has already been proven by the 
change in volume and in vapor density, which occurs when 
oxygen is transformed into ozone, or when the reverse 



228 CHEMISTRY 

change takes place. A molecule of oxygen consists of 2 
atoms, and its vapor density is 16, whereas the molecule of 
ozone consists of 3 atoms, and its vapor density is 24. 

332. Ozone. — Oxygen is best converted into ozone by 
subjecting it to the silent discharge of an induction coil. 
It is also converted into ozone by the electrolysis of dilute 
sulfuric acid, and by the slow oxidation of phosphorus. 

Prepared by either of these methods the ozone is very- 
dilute, rarely forming more than one-fifth of the whole. 
Ozone has a strong odor, somewhat resembling that of 
chlorin; it irritates mucous membranes, and quickly 
induces headache. At — 106° it condenses to a dark blue 
liquid ; it is more energetic chemically than oxygen, quickly 
bleaching, disinfecting, and even destroying organic sub- 
stances by oxidation. Many metals not affected in oxygen 
are attacked by ozone. Ozone is sometimes considered as 
oxygen oxid, 2 0. It often acts as a reducing agent, taking 
oxygen from other substances and changing to the ordinary 
form of oxygen, 

03 + = 20,. 

This is believed to be its action on the blood. Ozone is 
produced in air by lightning discharges, and is usually 
present in country air. Its characteristic odor proves its 
presence also in the air near a static electric machine. 

REVIEW QUESTIONS 

1. Describe the preparation of phosphorus. State the properties 
and two important uses of phosphorus. 

2. Describe an experiment illustrating the affinity of phosphorus 
for iodin. 

3. Explain the difference between the chemical action of the 
ordinary friction match and that of the safety match, stating the sub- 
stances from which each is made. 



PHOSPHORUS 229 

4. Describe a method of preparing phosphoric acid. Give the 
names, formulas, and methods of preparation of two acids formed 
from phosphoric acid. 

5. Give the name and properties of the substance formed by the 
union of phosphorus pentoxid and hot water, and write the reaction. 

6. Discuss allotropism. Illustrate by phosphorus and carbon. 

7. Contrast the characteristics of two forms of phosphorus. 

8. Mention two forms of oxygen. State the difference between 
them, and state a theory to account for the difference in their effects. 

9. Give the name and formula of a monobasic acid, of a dibasic 
acid, of a tribasic acid. Give the names and formulas of salts formed 
by the acids named. 

10. Define tribasic acid, and give an example with formula. 
Classify as normal or acid three salts formed from this acid, and give 
the formula of each. 

11. "Write the name and formula of a normal salt, an acid salt, a 
double salt. Show how these three classes of salts are related to one 
another. 

12. Describe the chemical changes which occur when phosphorus is 
burned in oxygen and the product dissolved in water. 

13. State an objection to the use of the term acid salt. 

14. In what respects are the properties of ozone similar to those of 
chlorin ? 



CHAPTER XXXI 
ARSENIC 

Symbol As. — Atomic Weight 75 

333. Occurrence. — Arsenic is found free in nature, "but 
occurs much more abundantly in combination with other 
elements. Its principal ores are arsenolite, As 2 3 ; realgar, 
As 2 S 2 , the red sulfid ; orpiment, As 2 S 3 , the yellow sulfid ; 
arsenopyrite (mispickel), FeSAs ; and arsenical iron, FeAs 2 . 

334. Preparation. — Arsenic is obtained as a by-product 
in the process of reducing certain ores, but most of the 
arsenic of commerce is obtained from arsenopyrite. The 
ore is heated in covered iron pots, out of contact with 
the air, when the arsenic vaporizes without visible lique- 
faction and condenses as a steel-gray powder on the cooler 
portions of the apparatus. 

335. Properties. — Arsenic is a very brittle steel-gray 
substance, having a metallic lustre ; it is a good conductor 
of heat and electricity. At ordinary pressures it cannot 
be melted, but passes directly into the aeriform state. If 
heated in a sealed tube under great pressure, however, it 
may be liquefied. At low temperatures its vapor density 
shows that, like phosphorus, it is tetratomic, but at high 
temperature it is diatomic; it exists in at least two allo- 
tropic forms, a crystal and an amorphous substance, either 
of which is readily transformed into the other. It burns in 
oxygen with a bluish flame. It will be observed that its 

230 



ARSENIC 231 

physical properties resemble those of a metal, and in some 
of its chemical properties it is like a metal ; for example, it 
combines with the members of the chlorin family and forms 
alloys with the metals ; its oxids, however, are acid-forming, 
and in several other chemical properties it resembles the 
acid-forming elements. It is one of the elements which lie 
between the metallic and the non-metallic elements which 
are known as metalloids. The addition of a small amount 
of arsenic to a metal increases its fluidity in the liquid state 
and increases its hardness when in the solid state; it is 
therefore added to lead which is to be made into shot. 

336. Compounds of Arsenic and Oxygen. — Two compounds 
of arsenic and oxygen are known, arsenious oxid, As 4 6 , and 
arsenic oxid, As 2 5 . The formula of the first was formerly 
written As 2 3 , and it was known as the trioxid, but it has 
been proven that its vapor density is 198, which corresponds 
with the formula As 4 6 . Arsenic oxid is unimportant, and 
will not be discussed. 

337. Arsenious Oxid, As 4 6 . — This is the principal com- 
pound of arsenic known in commerce ; it is commonly 
known as arsenic, or more rarely as white arsenic or as 
arsenious acid. 

As has been stated, this substance occurs in nature. It 
may be prepared by heating metallic arsenic or an arsenical 
ore in a stream of oxygen or air and condensing the vapors. 
Arsenious oxid occurs in three forms : — 

1. An amorphous, vitreous mass, somewhat more soluble 
in water than the other varieties, which gradually changes 
to the second form. 

2. An octohedral crystal, which is converted into the 
amorphous modification by fusion. 



232 CHEMISTRY 

3. A prismatic crystal. 

The amorphous modification dissolves sparingly in water, 
requiring 108 parts ; its solubility is somewhat increased by 
acidulating the water with hydrochloric acid. 

Arsenious oxid is a violent poison ; a dose of two deci- 
grammes usually proves fatal, but men employed in arsenic 
works and habitual users of arsenic often take much larger 
doses without apparent injury. The fact that arsenious 
oxid has neither taste nor smell accounts for its use in so 
large a proportion of the cases of criminal poisoning. 

The water solution of arsenious oxid has a feeble acid reaction, 
which is probably due to the presence of a small quantity of arsenious 
acid, but the acid has never been isolated. Three classes of salts of 
this unknown acid are readily obtained ; they are known as ortho- 
arsenites, meta-arsenites, and pyro-arsenites, and correspond to the 
three classes of salts formed by phosphoric acid. 

Arsenious oxid is used in making certain pigments, as Scheele's 
green, CuHAs0 3 , and Schweinfurt green, a compound of the arsenite 
and acetate of copper commonly called Paris green. It is also used as 
an oxidizing agent in glass making ; in very small doses it is used in 
medicine, and small quantities are consumed each year in the prepara- 
tion of vermin poisons. 

Compounds which, like arsenious oxid, exist in two or 
more forms which are identical in percentage composition 
and molecular weight, but which differ in physical or chem- 
ical composition or both, are said to be isomeric and the 
phenomenon is known as isomerism. 

Compounds which are identical in percentage composition 
but which differ in molecular weight and properties are said 
to be polymeric and the phenomenon is known as pohjmerism. 
Acetylene, C 2 H 2 , and benzene, C 6 H 6 , are polymeric. 

338. Hydrogen Arsenid, AsH* (Arsin). — Like nitrogen, 
phosphorus and arsenic each furnish a gaseous compound 



ARSENIC 233 

containing three atoms of hydrogen. The arsenic com- 
pound is important because it gives ns one of onr more 
valuable tests for arsenic. 

Hydrogen arsenid is formed when a soluble arsenic com- 
pound is acted upon by nascent hydrogen. It is a colorless 
gas with a strong, repulsive odor, extremely poisonous even 
when very dilute, more than one chemist having lost his 
life through the accidental inhalation of the gas. It may 
be liquefied at — 40°, it burns with a bluish white flame, 
evolving fumes of arsenious oxid. If the gas be passed 
through a solution of silver nitrate, metallic silver is pre- 
cipitated and the arsenic is found in the solution. 

Experiment CXXII. Marsh's test for arsenic. — 1. Fit a small 
flask with a two-holed stopper, c, carrying a safety tube in one hole 
and a delivery tube drawn out to a point in the other. 

2. Put a few pieces of zinc in the flask, cover them with water, 
and add dilute hydrochloric acid until brisk effervescence occurs. 

3. Holding the flask in the hand, collect the evolved hydrogen over 
water in a test bottle. Test each bottle of the gas obtained. 

4. When the air is expelled from the apparatus and the gas burns 
quietly, pour a few drops of a solution of arsenious oxid through the 
safety tube, ignite the gas and hold a concave piece of porcelain, as 
a piece of an evaporating dish, in the flame. Keep the gas alight. 
Describe the deposit formed on the porcelain. 

Soluble compounds of antimony form a similar deposit 
which has no lustre and is blacker ; but the antimony spot 
dissolves in ammonium sulfid, whereas that of arsenic does 
not dissolve unless heated. There is no substance which 
can be identified by the chemist more positively than 
arsenic. The Harsh test will detect the slightest trace 
of the poison. 

339. Complete and Incomplete Combustion. — The princi- 
ples developed in § 272, p. 170, explain the formation of 



234 CHEMISTRY 

the arsenic "mirror." When arsin burns normally, the 
following reaction occurs : — 

4 AsH 3 + 6 2 = As 4 6 + 6 H 2 0. 

When a cold object is held in the flame, thus excluding 

the air and lowering the temperature of the flame below 

the kindling temperature of arsenic, the following reaction 

occurs : — 

4 AsH 3 + 3 2 = As 4 + 6 H 2 0. 

There are many cases similar to the above ; the prepara- 
tion of lampblack, § 270, is one of them. When marsh gas 
burns in air the following reaction occurs : — 

CH 4 + 2 2 = C0 2 + 2 H 2 0. 

In a limited supply of air the reaction is approximately 
as follows : — 

CH 4 + 2 = C + 2 H 2 0. 

Similarly, the perfect combustion of hydrogen sulfid and 
carbon disulfid are expressed by the following equations : — 

H 2 S + 3 = H 2 + S0 2 , 
CS 2 + 3 2 = C0 2 + 2 S0 2 , 
and the incomplete combustion by the following : — 
H 2 S + = H 2 + S, 

CS 2 + 2 = C0 2 4- 2 S. 

REVIEW QUESTIONS. 

1. In what compound is the element arsenic found in nature ? 
What are its properties ? 

2. What compound does arsenic form with hydrogen ? To what 
compound of nitrogen is it analogous ? How is it formed ? 

3. What is the substance which is usually called arsenic ? I low is 
it obtained from the element arsenic, and from the compounds of 
arsenic with metals ? What are its properties ? 



ARSENIC 235 

4. State the properties and uses of arsenic, and describe a process 
for obtaining it. 

5. Describe the characteristics and process of manufacture of 
arsenious oxid. 

6. Explain why so many substances unite with the sulfur of hydro- 
gen sulfid more readily than they do with free sulfur. 

7. Describe Marsh's test for arsenic. 

8. Compare the formation of the metallic mirror, of Marsh's test 
for arsenic, with the deposition of soot on a cold body held in a candle 
flame. 

9. Compare the products of the complete combustion of hydrogen 
arsenid with the products formed when the combustion is rendered 
incomplete by holding a cold porcelain dish in the flame, writing the 
reactions in both cases. 



CHAPTER XXXII 
QUALITATIVE ANALYSIS 

340. Apparatus. — For this work the following additional 
apparatus will be required : — 

6 test tubes 2 small breakers 

1 evaporating dish 1 wash bottle 
filter paper 1 test-tube stand 

2 funnels 1 pair forceps 
1 sand bath litmus paper 

8 reagent bottles, 150 or 200 cc. 
(Keep litmus paper in small box or bottle.) 

341. Reagents. — The solutions used in analysis should 
be prepared by each student from chemically pure substances 
dissolved in distilled water. See that the bottles are clean. 

Experiment C XXIII. — Prepare 150 cc. of each of the following 
reagents : — 

Hydrochloric acid, 1 part acid to 4 parts water. 
Nitric acid, 1 part acid to 4 parts water. 

Ammonium hydroxid, 1 part 26° ammonia water to 3 parts w T ater. 
Ammonium sulfid, the above saturated with hydrogen sulfid. 
Ammonium carbonate, 1 part to 4 of water + 1 part ammonium 
hydroxid. 

Ammonium chlorid, 1 part to 8 of water. 
Sodium hydroxid, 1 part to 8 of water. 
Sulfuric acid, concentrated. 

342. Suggestions. — 1. Keep all apparatus clean; rinse it with 
water, using brush when necessary. If not cleaned with water, try 
concentrated nitric or nitrohydrochloric acid. Never use brush with 

236 



QUALITATIVE ANALYSIS 237 

acids. Tubes may be cleaned in one-fourth the time if not allowed to 
stand till dry. 

2. Hold test tubes in fingers when heating them ; keep the tubes 
moving. 

3. Never lay the stoppers of reagent bottles down. Hold them be- 
tween the little finger and the palm and replace them promptly ; this 
avoids mixing reagents. 

4. When applying reagents, hold the tubes on a level with, the eye 
and add the reagent, a drop at a time. 

5. You will have enough to do without attending to the work of 
your neighbor. 

6. You are responsible for the good order of your locker, drawer, 
and table. The table must be left clean and dry at the close of each 
period. 

7. All solid matter to be thrown away must be deposited in jars. 
If thrown in the sink the waste pipe will become clogged. 

8. Never carry reagent bottles from the side table to your table 
but use them at the side table and replace them. 

343. Precipitates. — A precipitate is a substance which 
falls to the bottom of the vessel containing a solution, on 
the addition of some other substance capable of producing a 
chemical change. Chemical changes may occur when solu- 
tions are mixed, without forming precipitate, if all of the 
products of the reaction are soluble in the liquid. When 
a precipitate is formed, however, it is always evidence of 
chemical change, and when one of the products is a solid, 
it may be separated from the substances in solution by 
filtration. For this reason one of the systems of quali- 
tative analysis is based upon the formation of precipitates 
when the substance to be analyzed is treated with certain 



344. Grouping of the Metals. — In order to determine 
which of the common metals forms precipitates when 
treated with various reagents, test four or five cubic centi- 
metres by adding the reagent drop by drop. If the sub- 



238 CHEMISTRY 

stance is not in solution, it will be necessary to dissolve it 
before beginning the analysis. 

Experiment CXXIV. — 1. Determine which of the following metals 
are precipitated by hydrochloric acid. 

2. Record the color of the precipitate and write the reaction. 

3. Test at least one salt of each of the following metals : — 

Aluminum Lead 

Antimony Magnesium 

Ammonium Manganese 

Arsenic Mercury (ous) 

Barium Mercury (ic) 

Bismuth Nickel 

Cadmium Potassium 

Calcium Silver 

Cobalt Sodium 

Chromium Strontium 

Copper Tin (ous) 

Iron (ous) Tin (ic) 

Iron (ic) Zinc 

Your notes should have the form : — 

Copper sulfate No precipitate 

Calcium chlorid No precipitate 

Silver nitrate White precipitate 

AgNOs + HC1 = AgCl + HNQg. 

The precipitate is indicated by underlining the formula. Which of 
the elements tested form insoluble chlorids ? Which may be sepa- 
rated from the rest by the action of hydrochloric acid ? These ele- 
ments constitute the first group. 

Experiment CXXV. To determine which of the common metals 
form sulfide which are insoluble in acidulated water. — Test each of 
the metals in the above list as follows : Add a few drops of hydro- 
chloric acid to give the solution an acid reaction, then add a solution 
of hydrogen sulfid drop by drop, and heat. Which bases are precipi- 
tated ? Which bases form light-colored precipitates? Which bases 



QUALITATIVE ANALYSIS 239 

form dark-colored precipitates ? What sulfids are insoluble in acidu- 
lated water ? These constitute the second group. What constituent 
of the hydrogen sulfid enters into these precipitates ? 

Experiment CXXVI. To determine which of the common bases 
form sulfids ivhich are insoluble in free ammonium hydroxid (hydro- 
gen sulfid is an acid, hence it is best to use one of its salts as the 
reagent). 

1. Test each of the bases included in the above list as follows : — 

2. Add ammonium hydroxid until the solution has an alkaline 
reaction, then add ammonium sulfid. Which bases are precipitated 
by ammonium hydroxid alone ? which by ammonium hydroxid and 
ammonium sulfid ? Of the latter bases, which is not precipitated 
when ammonium chlorid is present in excess ? 

It is more convenient to exclude from the third and 
fourth groups the substance not precipitated in the pres- 
ence of ammonium chlorid. We therefore add an excess of 
this reagent to the solution under examination, thus throw- 
ing this substance, which would otherwise appear in the 
third group, into the fifth group. Which sulfids are in- 
soluble in an alkaline menstrum ? Which elements belong 
to the third group ? 

Experiment CXXVIL To determine which of the common bases 
form carbonates ivhich are insoluble in an alkaline menstrum. — Test 
at least one substance containing each metal mentioned on page 229, 
as follows : Add ammonium hydrate until the solution has an alka- 
line reaction, then add ammonium carbonate. What bases are pre- 
cipitated ? What carbonates are insoluble in alkaline water ? Which 
are soluble ? What bases are precipitated by ammonium carbonate 
and not by ammonium sulfid ? If the bases included in the first three 
groups had been removed from the solution, which of the remaining 
would be precipitated by ammonium carbonate ? Of these, which is 
not precipitated when ammonium chlorid is present in excess? If 
you had a solution containing silver and calcium, how could you 
separate them ? How could you separate lead, copper, and iron ? 
Cadmium, barium, and potassium ? How could you separate sodium, 
potassium, and ammonium from all the others tested ? Make a list of 
the elements tested, dividing them into five groups. 



240 



CHEMISTRY 



Fill out the following table in your note-book, writing the symbols 
of the metals of each group in appropriate column : — 

Grouping of the Metals 



To solution containing any metal add HC1 



Precipitate 
Group I 



Filtrate ; add H 2 S 



Precipitate 
Group II 



Filtrate ; addNH 4 HO + NH 4 Cl-KNII 4 ) 2 S 



Precipitate 
Group III 



Filtrate ; add 

NH4HO + (NH 4 ) 2 C0 3 



Precipitate 
Group IV 



Filtrate 
Group V 



ANALYSIS OF AN UNKNOWN SUBSTANCE 
345. Preparing the Solution. — The scheme of analysis, 
based upon the facts brought out in the experiments just 
completed, is known as the ivet process to distinguish it 
from the process based upon tests applied directly to the 
solid substance, which is known as the dry process. The 
wet process requires that the substance under examination 
be dissolved in some solvent before any reagents are added. 
This solution should be transparent and free from solid 
particles, and should be obtained by the complete solution 
of a portion of the substance, as this is the only way that 
one can be sure that all the substances in a mixture are 
tested. If the substance under examination is a solid, put 
a small amount of it in a test tube with 2 or 3 cc. of distilled 
icater ; if it does not dissolve, apply heat; if this fails, add 
a few drops of concentrated hydrochloric acid, and boil the 
substance a short time. If the substance is insoluble in 



QUALITATIVE ANALYSIS 241 

acidulated water, pour off the liquid and try strong hydro- 
chloric acid; if this fails to dissolve it, add one-third as 
much strong nitric acid as you have of the hydrochloric (2). 
If the substance is insoluble in the aqua regia thus formed, 
it must be fused with sodium carbonate on platinum foil (3). 

Notes. — 1. If a white residue is obtained here that resembles 
silver or lead chlorid, treat a fresh portion of the substance with nitric 
acid. 

2. If much strong hydrochloric acid has been used, or if any nitric 
acid has been added, it is necessary to evaporate to dryness before 
passing to group 2. (See note 1, article 352.) 

3. Place a small quantity of the original substance on a piece of 
platinum foil or a piece of porcelain ; cover it with 5 or 6 times its 
volume of sodium carbonate, and heat before the blowpipe until the 
effervescence has ceased and the mixture is fused to a thin liquid ; 
this may require 10 or 15 minutes. Boil the fused mass with water ; 
filter and wash any residue ; dissolve a portion in dilute nitric acid, 
and test for group 1. Dissolve the remainder in dilute hydrochloric 
acid. Save a portion of the water solution for acid tests, and pour the 
remainder into the hydrochloric solution, and test for metals as usual. 

346. As a precipitate is a solid, it may be collected on 
filter paper. The filtrate, as the filtered liquid is called, 
may contain more of the metal which was precipitated 
if the reagent was used sparingly, and as this may inter- 
fere with subsequent test, the student should always test 
the filtrate with a drop or two of the reagent which formed 
the precipitate. If a precipitate is again formed, pour the 
filtrate on the filter again, repeating the process until 
certain that all of the metal has been removed. Much 
unnecessary work may be saved if the student will remem- 
ber that reagents lose their characteristic properties when 
they take part in a chemical change; therefore, we may 
be certain that enough of a reagent, having an odor or a 
color, has been added to entirely remove any metals which 
it can precipitate, when the liquid tested has acquired the 



242 CHEMISTRY 

odor or the color of the reagent. It is hardly necessary 
to add that the above statement does not apply to those 
cases in which an excess of the reagent is required, either 
for the complete precipitation of the substance which is 
required in the solid state, or to prevent the precipitation 
of some substance which we wish to keep in solution. We 
are certain that enough hydrogen sulfid, ammonium sulfid, 
or ammonia has been added when the odor of the reagent 
can be detected in the liquid. 

347. Washing Precipitates. — The success of the student 
in qualitative analysis will largely depend upon the atten- 
tion which he pays to the directions given in the preceding 
paragraph, the care with which he washes his precipitates, 
and the purity of his reagents. The chief end to be at- 
tained by the precipitation of a substance is its separation 
from other substances ; hence, precipitates must be washed 
until they are entirely free from the liquid in which they 
were formed. Precipitates are usually washed on the filter. 
After the filtrate has all passed through the filter paper 
add 1 or 2 cc. of water from the wash bottle; the jet 
should strike the filter paper near the upper edge, so that 
the precipitate may be carried down to the apex of the 
filter. When all of the wash water has passed through, 
repeat the process. Much time may be saved by washing 
precipitates with several small quantities of water rather 
than fewer large quantities. 

It is not enough to think that the washing is sufficient; 
the student must know. Washing should be continued as 
long as the wash water gives a test for any substance 
known to be in filtrate; e.g. first group precipitates should 
be washed until the wash water does not redden blue litmus 
paper, showing absence of hydrochloric acid. 



QUALITATIVE ANALYSIS 243 

348. The Analysis. — Every analysis is begun by testing 
for group one, as directed in § 349, and passing to sub- 
sequent articles as directed. If it is known that only one 
substance is present, tlie filtrate remaining when the group 
precipitate is filtered out may be discarded. 

THE EIEST GROUP 

349. Precipitation. — (a) If the solution is alkaline or 
neutral, add nitric acid to distinct acid reaction (1). 

(b) Add dilute hydrochloric acid, drop by drop, as long 
as a precipitate is formed (2), (3). 

(c) Filter and treat the precipitate as directed in § 351. 

(d) If metals, not in the first group, may be present, the 
filtrate must be treated as directed in § 352. 

(e) If no precipitate is obtained, treat the solution as 
directed in § 352. 

Notes. — 1. The solution must have an acid reaction before the 
analysis is begun, as many members of the subsequent groups which 
are soluble in alkaline solution are precipitated when the solution is 
acidified, and would, therefore, mislead the student. 

2. Avoid the excess of hydrochloric acid, and do not use the con- 
centrated acid. 

3. Dilute hydrochloric acid sometimes precipitates bismuth and 
antimony here, but the precipitate dissolves when more of the acid is 
added. If in doubt, test a separate portion of the original solution 
with a drop of concentrated hydrochloric acid ; if no precipitate is 
formed, no first group element is present. 

350. Separation of the First Group Metals. 

Experiment CXXVIII. — Examine a filtered and washed precipi- 
tate of each first group metal to determine which chlorid is soluble 
in hot water and how each is affected by ammonium hydroxid. How 
could you determine which of the first group metals in an unknown 
solution containing one of them ? If a solution contained silver and 
lead, how could you separate them ? 

These properties enable us to separate the first group 
metals, and to prove the presence or absence of either of them. 



244 



CHEMISTRY 



Experiment CXXIX. — 1. Pour about 1 cc. of a solution of each of 
the following nitrates into a test tube : (a) silver nitrate, (6) plumbic 
nitrate, (c) mercurous nitrate. 

2. Precipitate as directed in § 349. 

8. Follow the directions in § 351 ; endeavor to find a reason for 
each step. 



351. 



Analysis of Group I 



Wash the precipitate with cold water, using as little as possible ; 
then treat with much hot water. Why ? See notes (1) and (2). 



Residue = AgCl or HgCl or both 
Add NH 4 OH 


Solution, PbCl 2 
Confirm by testing 


Three 


Residue — black, 
- NH 2 Hg 2 Cl 


Solution — AgCl 
Add HNO3 to acid 
reaction 


Portions of the somuon < 
follows : 


Hg present 


add 
H 2 S0 4 
to one 
part 


add 
H 2 Sto 
another 


add 
K 2 Cr0 4 

to an- 
other 




Precipitate 
= AgCl 
Ag present 


Lead may occur 


Precipitate 
Pb present 


here as white pre- 
cipitate 


white 
PbS0 4 


black 
PbS 


yellow 
PbCrC-4 



Notes. — 1. Lead is not always precipitated in this group. 

2. If the lead chlorid is not entirely dissolved by the hot water, 
the addition of the ammonium hydroxid changes what remains to a 
basic salt (white) ; this often passes through the filter, rendering the 
filtrate turbid. Nitric acid makes it clear again. 



THE SECOND GROUP 

352. Precipitation. — (a) Heat the filtrate from the first 
group (1), pass hydrogen sulfid through it as long as the 
precipitate increases (2), (3), or until the solution smells 
strongly of the gas. 

(b) Heat to boiling, allow the precipitate to settle (4). 



QUALITATIVE ANALYSIS 245 

(c) Filter and wash the precipitate with hot water as 
long as the wash water reddens blue litmus (5). 

(d) Dilute a portion of the filtrate with two or three 
times its volume of water and test again with hydrogen 
sulfid (6). If a precipitate is obtained, dilute the whole of 
the filtrate and treat with the group reagent until complete 
precipitation is secured. Pour on the filter paper contain- 
ing the balance of the precipitate. 

(e) If no precipitate is obtained, or if the filtrate may- 
contain metals of subsequent groups, pass to § 357. 

(/) Treat the group precipitate as directed in § 354. 

Notes. — 1. Hydrogen sulfid will not precipitate the second group 
metals from a solution containing much nitric acid or aqua regia. If 
either of these acids was used in dissolving the substance, evaporate 
to dryness in an evaporating dish, dissolve the residue in water con- 
taining a little hydrochloric acid, and pass the hydrogen sulfid through 
this solution. 

2. If the solution contains a strong oxidizing agent, e.g. a nitrate, 
chlorate, chromate, or a ferric salt, a white precipitate of free sulfur 
is obtained. 

3. Change of color from red to green, or from a colored to a color- 
less solution, does not indicate a second group substance. The former 
change is probably due to the presence of a chromate, the latter to a 
ferric salt. There are no white precipitates in the second group. 

4. Some compounds of arsenic are precipitated very slowly from 
a cold solution, and rather slowly from a hot solution. Should a 
yellow precipitate form slowly, heat the solution nearly to boiling 
during the precipitation. 

5. All traces of acid must be removed before proceeding to the 
separation of the metals of this group. 

6. The second group metals must be entirely removed before pro- 
ceeding to the next group. As the presence of too much hydrochloric 
acid sometimes prevents complete precipitation, it is best to dilute the 
filtrate before the final test. 

353. The Sub-groups. 

Experiment CXXX. — 1. Determine which of the eight sulfids pre- 
cipitated in this group are soluble in yellow ammonium sulfid. 



246 



CHEMISTRY 



2. Filter each precipitate, wash, and pour the yellow ammonium 
sulfid on the paper. Notice whether any of the precipitate is dis- 
solved. It is not always necessary to wait for it all to dissolve. The 
three metals which are soluble constitute the tin sub-group, the others 
are the copper sub-group. 

354. The Separation into Sub-groups. — a. Make a hole 
in the bottom of the filter paper and wash the precipitate 
through it into a test tube, using as little water as possible. 

b. Warm the precipitate in the test tube with yellow 
ammonium sulfid, and filter again. 

c. The filtrate will contain the metals of the tin sub- 
group, and the precipitates those of the copper sub-group. 

d. Treat the filtrate as directed in § 356, if a substance 
belonging to this group may be present. 

e. Treat the precipitate as directed in § 355. 

355. Separation of the Metals of the Copper Sub-group. 

Directions 



Precipitate (1), HgS, PbS, Bi 2 S 3 , CdS, CuS 
Boil with HNO3 (2). Replace evaporated acid 



Residue 
Dissolve in 
HC1 and KCIO; 
Add SnCl 2 
Precipitate HgCl 2 
Hg present 



(4) 



Precip. 
= PbS0 4 
Pb present 



Solution Pb(N0 3 ) 2 , Bi(N0 3 ) 2 , Cu(N0 3 ) 2 , 
Cd(N0 3 ) 2 . Add H0SO4 (5) 



Filtrate Bi, Cd, and Cu salts. 
NH4OH (6) 



Add 



Precip. 
= Bi0 3 H 3 
Dissolve 
in HC1 (7) 
pour into 
water 
Precip. (8) 
BiOCl 
Bi present 



Filtrate Cd and Cu. Add 
KCN and H 2 S (9) 



Precip. 

CdS (10) 
Cd present 



Solution (11) 
KCN CuCN 
Cu present 



QUALITATIVE ANALYSIS 241 

Notes. — 1. If the precipitate has "been exposed to the air for some 
time, it should be washed with a few drops of yellow ammonium sulfid 
and then with water before treating with nitric acid. Wash until wash 
water is neutral. 

2. Transfer the precipitate to an evaporating dish for this operation ; 
boil for several minutes or until dissolved ; filter and wash the residue, 
if any. 

3. If too little nitric acid was used, other sulfids than that of mercury 
may occur here. The stannous chlorid test should therefore always be 
tried. Mercury sometimes occurs here as a yellow residue. 

4. Use only a small crystal of potassium chlorate and boil until the 
vapor no longer bleaches litmus paper before adding the stannous 
chlorid. 

5. To the filtrate from the mercuric sulfid add about 5 cc. of strong 
sulfuric acid and boil in an evaporating dish until white fumes appear 
(this proves that nitric acid has been expelled). When cool, dilute to 
ten volumes and transfer to a beaker ; filter if turbid. 

6. Add ammonium hydroxid to slight alkaline reaction. Then if a 
precipitate appears, a small quantity more to redissolve any copper or 
cadmium that may be precipitated ; heat gently and filter. 

7. Wash the precipitate, then pour a little strong hydrochloric acid 
on the filter ; catch it in an evaporating dish and evaporate the solution 
until only a few drops remain ; pour these into a beaker of water. 

8. Failure to follow the directions in note 5 will cause a precipitate 
of lead to appear when ammonium hydroxid is added, hence, the con- 
firmatory test should always be tried. 

9. If the filtrate from the bismuth hydroxid is distinctly blue, we 
may conclude that copper is present and test for cadmium with potas- 
sium cyanide and hydrogen sulfid. If not blue, the following more 
sensitive test for, copper should be applied. Acidify a small portion of 
the filtrate with acetic acid and add potassium ferrocyanidE4Fe(CX) 6 ; 
a reddish brown precipitate indicates copper. 

10. A yellow solution does not prove the presence of cadmium, but 
a yellow precipitate does. 

11. Test this, or the original solution, with metallic iron ; if copper 
is present, it will be deposited on clean surfaces. 

356. Separation of the Tin Sub-group. — Add dilute hydro- 
chloric acid to the ammonium sulfid solution to slight acid 
reaction; filter, dry the precipitate by suction, reject the 
filtrate, and treat the precipitate as directed below. 



248 



CHEMISTRY 



Precipitate As 2 S 5 , Sb 2 S 5 , SnS 2 . Add concentrated HC1 (1) 



Residue (2) 
AsaSg 
Dissolve in 
HC1 + KCIO3 (3) 
Add NH 4 OH (4) 
NH4CI + MgCl 2 
Precip. (3) 
MgNH 4 As0 4 
As present 



Solution SbCl 3 , SnCl 4 

Place in hydrogen generator (6) 

Collect gas in solution of AgN(>3 (7) 



Gen~erator(8) 
Residue Sn 
Dissolve in 
strong HC1 
Add HgCl 2 
Precip. (9) 
HgCl 

white to gray 
Sn present 



AgN0 3 Solution (10) 



Precip. Ag, Sb 
Digest with warm 
HC1 and dilute (11) 
Divide 



Add H 2 S 
Precip. 
orange 
Sb 2 S 5 



Add H 2 
Precip. 

white 
SbOCl 



Sb present 



Filtrate 

H 2 As0 3 

Add HC1 (12) 

Filter (13) 

Add H 2 S 

Precip. 

yellow 

As 2 5 

As present 



Notes. — 1. Heat gently in an evaporating dish as long as paper 
moistened with lead acetate is blackened by the vapors ; add a little 
water and filter. 

2. Wash the residue on the filter, then dissolve, using very little 
potassium chlorate. 

3. Heat to expel the excess of chlorin. 

4. Add ammonium hydroxid till alkaline, filter, if necessary, add 
half as much more ammonium hydroxid as you have of the solution, 
then add magnesia mixture, agitate, and set aside for 24 hours if no 
precipitate appears at first. 

5. This precipitate is slightly soluble in water, and to a less extent 
in ammonium hydrate, hence traces of arsenic are likely to be lost 
unless the solution (3) is concentrated. 

6. Place some strips of platinum, and a few small pieces of zinc 
known to be free of arsenic, in a test tube ; add dilute hydrochloric acid 
and the solution to be tested ; quickly insert stopper carrying a delivery 
tube, which shall conduct the gas through a solution of silver nitrate. 

7. The gas evolved may be a poisonous one, and must not be 
inhaled. If tin was present, it will be found in the generator, which 
must be examined as directed in Note 8. If antimony was present, 
it will form a precipitate in the silver solution. Some arsenic 
may have been dissolved in the concentrated hydrochloric acid (1), 



QUALITATIVE ANALYSIS 249 

in which case it will be found here dissolved in the silver nitrate 
solution. 

8. When the zinc has dissolved, pour the contents of the generator 
on a filter. Wash thoroughly, then dissolve the residue in strong 
hydrochloric acid. 

9. The formation of a white or gray precipitate here proves the 
presence of tin, because the stannous chlorid which is formed when 
tin is present reduces the mercuric chlorid to mercurous chlorid, or to 
metallic mercury. 

10. Filter and wash any precipitate in the silver solution. 

11. Do not dilute to precipitation before dividing into two portions. 

12. To remove silver, add hydrochloric acid, drop by drop, as long 
as a precipitate is formed, and filter. 

13. A yellow precipitate formed by the hydrogen sulfid proves the 
presence of arsenic. 

THE THIED GROUP 

357. Test for Phosphates. — If phosphates are present, the 
fourth group metals will be precipitated with those of the 
third group, and a more complicated method of separation 
must be used (1). 

The Test. — Boil a small portion of the second group 
filtrate to expel hydrogen sulfid, acidify with nitric acid, 
and pour it into two volumes of ammonium molybdate 
(NH 4 ) 2 Mo0 4 . 

Agitate, and allow to stand for some minutes ; if a yellow 
precipitate appears, phosphates are present, and the long 
process must be used. If phosphates are present treat the 
remainder of the second group filtrate as directed in § 362. 

If phosphates are absent, treat the filtrate as directed in 
§ 358. 

Note. — The above test, and the table in § 362, are given for the 
convenience of those teachers who wish to include this case in their 
course. Doubtless few teachers will care to give pupils in secondary 
schools metals of the third or fourth groups in the presence of 
phosphates. 



250 CHEMISTRY 

358. Separation into Sub-groups in the Absence of Phos- 
phates. — (a) The filtrate from the second group, from 
which all second group substances have been removed, is 
now boiled until the vapor no longer blackens paper mois- 
tened with lead acetate (absence of hydrogen sulfid) (1). 

(b) Add a few drops of nitric acid, and boil a short 
time (2). 

(c) Add ammonium hydroxid to slight (3) alkaline reac- 
tion (4). 

(d) Add decided excess of ammonium chlorid, say 15 or 
20 cc. (5), (6). 

(e) If a precipitate is obtained, a metal of the iron sub- 
group is present. Filter and wash any precijritate, and 
treat it as directed in § 359. 

(/) Treat the filtrate as directed in § 360. 

Notes. — 1. If no first or second group substance is present, time 
will be saved by taking a fresh portion of the original solution, which 
need not be boiled ; but this should not be done if the presence of a 
chromate was indicated when hydrogen sulfid was added (note 3, § 352) 
as the hydrogen sulfid reduces the chromium from its acid to its basic 
condition, and without this action the chromium would be detected 
only by the test for chromic acid. 

2. If iron is present, it must be in the ferric state ; boiling with 
nitric acid will transform it. 

3. If too much ammonium hydroxid is added, aluminum will be 
dissolved. 

4. If no precipitate is formed here, it proves the absence of inter- 
fering phosphates. 

5. Ammonium hydroxid precipitates magnesium, but the precipi- 
tate dissolves in ammonium chlorid. If an opaque white precipitate 
is obtained, indicating magnesium, pour a few drops of the liquid 
containing it into a test tube, add 5 or 6 times as much ammonium 
chlorid. If the precipitate dissolves, add enough ammonium chlorid 
to the rest of the liquid to dissolve it. 

6. The color of the precipitate indicates the metal present ; alumi- 
num is white and transparent ; chromium is blue-green ; iron is 
reddish brown. 



QUALITATIVE ANALYSIS 
359. Separation of the Iron Sub-group. 



251 



Precipitate = Fe 2 (OH) 6 , Cr 2 (OH) 6 , Al 2 (OH) 6 
Boil in evaporating dish with XaOH (1) 
Filter and wash any residue 



Precipitate = Fe 2 (OH) 6 , Cr 2 (OH) 6 
Divide in two parts 



Dissolve in dilute HC1 
(2), (3) 

Fe present 



II 
Fuse with Na 2 C0 3 

and KC10 3 (4) 
yellow mass = 
Cr present 



Filtrate = Xa 6 6 Al 2 
Acidify with HC1, and 

add NH4OH (5), 

white prec = 
Al present 



Notes. — 1. Add sodium hydroxid to alkaline reaction, then add 
5 or 6 cc. more, and boil several minutes. 

2. Dilute with water. To half of the solution add a few drops of 
potassium ferrocyanid, FHtFe(CX) 6 . A blue precipitate indicates 
iron. To the other half of the solution add potassium sulfocyanid, 
KCXS ; a blood-red color indicates iron. 

3. If iron is found, determine whether it is in the ferrous or ferric 
condition by testing portions of the original solution with potassium 
ferricyanid and with potassium sulfocyanid. 







Ferrous 


Ferric 


Potassium sulfocyanid 
Potassium ferricyanid 


no prec. 
blue prec. 
(dark) 


red solution 
green solution 
sometimes brown 





4. If chromium is present, a yellow mass of sodium chromate is 
obtained. To confirm, boil the fused mass in water, acidify with 
acetic acid, boil again, and add lead acetate ; a yellow precipitate 
confirms the presence of chromium. 

5. Add hydrochloric acid to acid reaction, then ammonium hydrate 
until alkaline, heat gently, and if no precipitate appears at once, set 
aside for half an hour. A flocculent white precipitate indicates 
aluminum. 



252 



CHEMISTRY 



360. Precipitation of the Cobalt Sub-group. — (a) To the 

filtrate from/, § 358, acid colorless ammonium sulfid, filter 
and wash the precipitate (1). Add a little ammonium sulfid 
to the wash water. 

(b) The filtrate must be tested for the metals of groups 4 
and 5. Pass to § 364. 

(c) Treat the precipitate as directed in § 361. 

Note. — The precipitate formed by cobalt and nickel is black, that 
of manganese is flesh color, but turns brown on standing, and that 
of zinc is white. 

361. Separation of the Cobalt Sub-group. 



Precipitate = CoS, MS, MnS, ZnS 
Dissolve on the filter with cold dilute HC1 (1) 
Receive the filtrate in an evaporating dish 



Residue — CoS, NiS 
(on filter paper) (2) 
Wash and dissolve in aqua 

regia (3) 
AddKCN (cone.) 



Precipitate (8) 


yellowish 


brownish 


green 


white 


insoluble in 


soluble in 


HC1 


HC1 


M present 


Co present 



Test by (4) 



Solution— ZnCl 2 , MnCl 2 

Add decided excess of NaOH, digest 

without warming 
Filter 



Prec Mii(OH) 2 
(5) Fuse with 
KN0 3 ,andNa 2 C0 3 
Green mass (6) 
Mn present 



Sol. Na 2 Zn0 2 
Add (NH 4 ) 2 S 
Prec. (7) 
Zn present 



Notes. — 1. Cobalt and nickel are often partially dissolved here, 
particularly if the acid is hot ; in such case they will be found with 
the manganese precipitate. 

2. If the hydrogen sulfid is not completely removed, zinc sulfid 
may be precipitated with the cobalt and nickel. 

3. If the residue is not abundant, incinerate the filter and dissolve 
the residue as directed. Boil the solution as long as the vapor bleaches 



QUALITATIVE ANALYSIS 253 

litmus paper before adding the concentrated solution of potassium 
cyanid. 

4. Tlie Borax Bead Test. — Heat a piece of platinum wire, the end 
of which is bent so as to form a small loop, dip it in powdered borax 
while hot and hold it in the flame again ; when the borax has melted 
and formed a transparent bead place some of the precipitate on it and 
heat again ; cobalt forms a blue bead, nickel in the oxidizing flame 
forms a red bead while hot, becoming colorless when cool. 

5. This precipitate must be tested for cobalt and nickel by the 
borax bead (-4) or with aqua regia and potassium cyanid, as in the 
table. 

6. Fuse on platinum foil or in a porcelain crucible, using six parts 
of the flux to one of the precipitate, continue heat until a thin liquid 
is obtained ; a green mass indicates manganese. 

7. To distinguish sulfur (from the group sulfids). Add hydro- 
chloric acid. Sulfur does not dissolve ; the sodium zincate does. 

8. If both cobalt and nickel may be present, filter and wash this 
precipitate and treat it with hydrochloric acid ; an insoluble residue 
indicates nickel. Confirm by the borax bead. 

362. Precipitation of the Third Group in the Presence of 
Phosphates. — (a) To the second group filtrate, from which 
all second, group substances have been removed and all 
hydrogen sulfid has been expelled, add ammonium hydroxid 
to slight alkaline reaction, then add decided excess of am- 
monium chlorid, and then ammonium sulfid as long as a 
precipitate is formed. 

(6) Heat to boiling and shake until the precipitate sub- 
sides quickly. 

(c) Filter and wash at once with water to which a little 
ammonium sulfid has been added. 

(d) Test the filtrate for the fourth* and fifth group 
metals. Pass to § 364. 

(e) Treat the precipitate as directed in § 363. 

* This is necessary even though phosphates be present, because 
there may not be enough of the phosphates to cause the precipitation 
of all of the fourth group metals present. 



254 



CHEMISTRY 



363. Separation of the Third Group Metals in the Presence 
of Phosphates. 



Precipitate AIO3H3, Cr0 3 FT 3 , CoS, MS, FeS, MnS, ZnS, Ba 3 (P0 4 ) 2 , 
Sr 3 (P0 4 ) 2 , Ca 3 (P0 4 ) 2 , MgXH 4 P0 4 
Treat with dilute HC1 (1) 



Residue 
CoS, MS 
Test for 
Co and Ni, 
as in § 361 



Solution A1C1 3 , CrCl 3 , FeCl 2 , MnCl 2 , ZnCl 2 . BaCl 2 . 
SrCl 2 , CaCl 2 , MgCl 2 
Divide in three parts 



I 
Add H 2 S0 4 and alcohol 



Precipitate 
BaSC-4 
CaS0 4 
SrS0 4 
(3) (4) 



Filtrate 

Reject 



II 

Boil with 
HX0 3 (5) 
and add 
K 4 Fe(CN) 6 
precipitate (6) 
Fe present 



III 
Treated as 
directed 
below 



Part III 



Boil with HN0 3 , add Fe 2 Cl 6 and BaC0 3 


(7) 






Precipitate 


Filtrate 


Fe0 3 H 3 , A10 3 H 3 , Cr0 3 H 3 
FeP0 4 (BaC0 3 ) 
Dissolve in HC1 and add 
H 2 S0 4 (8) 


Add NH 4 OH and (NH) 2 S 


Precipitate 

MnS, ZnS. 
Dissolve in HC1 


Filtrate 

Add (NH 4 ) 2 C0 8 

and (NH 4 ) 2 C 2 0, 


Precip. 
BaS0 4 

Reject 


Filtrate (9) 
Add NaOH and boil 


and add 
NaOH (14) 


Precip. 
Ba, etc. 
reject 


Filtrate 
(10) add 
Na 2 HP0 4 


Prec. 


Filtrate 


Prec. 


FlLT. 




Fe0 3 H 3 


Add HC1 


Mn0 2 H 2 


add H 2 S 




(17) 




Cr0 3 H 3 


andXH 4 OH 


Fuse 


Prec. 




Prec. 




(10) 


(12) 


(15) 


Zn pres. 




Mg pres. 




Cr pres. 


Al pres. 


Mn pres. 









Notes. — 1. Boil the solution until hydrogen sulfid is entirely- 
expelled. 

2. Evaporate the first portion to dryness, add a little dilute sul- 



QUALITATIVE ANALYSIS 255 

furic acid and twice as much alcohol ; set aside for a few minutes 
filter and wash with a little alcohol. 

3. Fuse on platinum foil with five parts of sodium carbonate. 
Boil with water, filter, and wash the precipitate. Dissolve in nitric 
acid and treat as directed in § 364. 

4. This solution may be added to filtrate from the third group if 
the filtrate contains fourth group metals. 

5. Boil the remaining portions in an evaporating dish with a little 
nitric acid, pour a little of it into a test tube, dilute and add two or 
three drops of potassium ferrocyanid ; a blue precipitate indicates 
iron. 

6. If iron is found, test the original solution as directed in note 3, 
§359. 

7. To the third portion in the evaporating dish (which has already 
been boiled in nitric acid) add ferric chlorid until a drop of the solu- 
tion on a piece of glass gives a yellow precipitate with ammonium 
hydroxid. Evaporate nearly to dryness to expel acid, then add 
sodium carbonate as long as the precipitate formed is redissolved by 
shaking. Pour into a flask, dilute to 200 cc, cool, and add barium 
carbonate (not too much) agitate frequently for half an hour. Eilter 
and wash the precipitate. 

8. Dissolve in dilute hydrochloric acid. Boil and add dilute sul- 
furic acid ; after a few minutes, filter ; throw the precipitate away. 

9. Add sodium hydroxid to strong alkaline reaction. Boil a few 
minutes and filter. 

10. Fuse the precipitate with sodium carbonate and potassium 
chlorate ; a yellow mass indicates chromium. Confirm by (4), § 359. 

11. Acidify the filtrate with hydrochloric acid, add ammonium 
hydroxid till slightly alkaline ; heat and set aside for half an hour if 
no precipitate appears at first. A precipitate indicates aluminum. 

12. Add a few drops of hydrochloric acid, and boil to expel car- 
bon dioxid. Then add ammonium hydroxid till alkaline, and add a 
small quantity of ammonium sulfid ; if a precipitate appears, filter and 
wash. 

13. The sodium hydroxid is added until the solution is alkaline. 

14. Test the precipitate for manganese as directed in note 6, 
§ 361. 

15. Concentrate the filtrate, add one-third its volume of ammonium 
hydroxid and a little disodic hydric phosphate. 

16. Stir with a glass rod, set aside for 24 hours if no precipitate 
appears at once. 



256 



CHEMISTRY 



THE FOURTH GROUP 

364. Precipitation. — (a) To the filtrate from the third 
group (1) containing ammonium chlorid, add ammonium 
hydroxid and carbonate ; heat gently for some minutes. 

(b) Filter out any precipitate, reserving the filtrate to be 
tested for the fifth group metals, § 366. 

(c) The precipitate is composed of fourth group metals, 
and is to be treated as directed below, § 365. 

365. Separation of the Fourth Group Metals. 

Precipitate. BaC0 3 , SrC0 3 , CaC0 3 
Wash and dissolve in dilute acetic acid 

Solution. Ba(C 2 H 3 2 ) 2 , Sr(C 2 H 3 2 ) 2 , Ca(C 2 H 3 2 ) 2 
To a small portion add K2C1O4 ; if a precipitate is formed, add to the 
whole and filter (2) 



Precipitate 


Solution. Sr(C 2 H 3 2 ) 2 , Ca(C 3 H 3 2 ) 2 


BaCr0 4 , yel- 


Add NH 4 OH and (XH 4 ) 2 C0 3 , filter and wash the 


low, soluble in 


precipitate. Dissolve it in HC1 


HC1 (3) 


Evaporate to dryness ; add H 2 (4) 


Ba present 


Divide into two portions 




I 


II 




Add CaS0 4 and 


Add K0SO4 (7) 




boil (5) 












Prec. (6), white 


Precipitate 


Filtrate 




Sr present 


Reject 


Add XH4OH and 

(XH 4 ) 2 C 2 4 
Precipitate (8) 
Ca present 



Notes. — 1. The filtrate from the ammonium sulfid precipitate 
should be colorless or light yellow. If brown or black, nickel is prob- 
ably present ; remove it by adding acetic acid to acid reaction, boiling 
and filtering ; if pink, chromium is indicated ; remove it by boiling 
and filtering ; a green color is due to traces of iron which settle to the 
bottom on standing. 



QUALITATIVE ANALYSIS 257 

If no precipitate is obtained in the preceding groups, the fourth 
group precipitate may he obtained by adding ammonium hydrate to 
the original solution, to alkaline reaction, then adding ammonium 
chlorid and carbonate. 

2. Before adding the potassium chromate, dilute the solution with 
30 cc. of water, heat to boiling, and add the chromate gradually. 

3. Precipitate again with sulfuric acid. A white precipitate insolu- 
ble in all acids confirms the presence of barium. 

4. This solution should be neutral to litmus. 

5. If a precipitate does not appear at once, set aside for ten minutes. 

6. Test by flame. The flame of strontium is crimson, that of 
barium yellowish green, and that of calcium yellowish red. 

7. Potassium sulfate must be added as long as a precipitate is 
produced in order to remove strontium, which would interfere with 
the test for calcium. Filter and reject any precipitate. 

8. This precipitate is insoluble in acetic acid, but dissolves in 
hydrochloric acid. 

THE FIFTH GROUP 

366. This group includes all the metals not precipitated 
in the preceding groups. Divide the filtrate from the 
fourth group into two portions, and test as directed below. 

1. To the first portion, add a little ammonium hydroxid, 
then enough ammonium chlorid to dissolve any precipitate 
that appears; then add sodium phosphate, Na 2 HP0 4 ; a 
white precipitate indicates magnesium (1) (2). 

2. Test the second portion by flame (3) (4). Violet, not 
obscured by blue glass, indicates potassium (5). Yellow, 
obscured by blue glass, indicates sodium. 

367. The Ammonia Test. — The original solution or solid 
substance should be tested for ammonium salts as follows. 

Place a small amount of the substance in a beaker, add 
solid calcium hydroxid, moisten with a little water. Cover 
the beaker with a glass plate, to the under side of which a 
piece of moist red litmus is attached. Heat gently. If 
ammonium is present, the vapor will turn litmus paper blue. 



258 CHEMISTRY 

Note the odor. (Care.) Hold the stopper of the hydro- 
chloric acid bottle over the beaker ; a white cloud will be 
formed if ammonium is present. Confirm by testing with 
Nessler's reagent, § 82. 

Notes. — 1. If calcium was found in the fourth group, traces may 
appear here ; to prevent interference with subsequent tests add 
ammonium oxalate (NH 4 ) 2 C204 to the fourth group filtrate and filter. 
If barium was found, remove it by precipitating with ammonium sul- 
fate and filtering. Reject the filtrate. Reject the precipitate in each 
case, and concentrate the filtrate until crystals appear, then test as 
directed. 

2. The magnesium precipitate is crystalline. If flocculent, it proba- 
bly consists of aluminum dissolved because too much ammonium 
hydroxid was used in precipitating the third group metals. 

3. If magnesium is abundant, it will interfere with the flame tests ; 
to remove it add barium hydroxid, filter, add dilute sulfuric acid to 
the filtrate, and filter again ; this filtrate will contain no magnesium. 

4. Evaporate the solution to dryness ; introduce a little of the resi- 
due into the flame of a Bunsen burner. 

5. Ignite a small portion of the residue on platinum foil to faint 
redness ; dissolve in the least possible quantity of water, add a few 
drops of hydrochloric acid, and the same amount of platinum chlorid, 
stir, and set aside a short time ; a precipitate indicates potassium. 

ACID TESTS 

368. The Removal of Bases. — Certain bases interfere 
with the acid tests; in cases in which the acid tests, 
§§ 369-373, are indeterminate the following directions 
should be followed. 

(a) The Substance is Soluble in Water. 1. If the sub- 
stance is in the fourth or fifth group, the original solution 
may be used for acid tests. 

2. If the substance contains metals of the first, second, 
or third group, add sodium carbonate as long as a precipi- 
tate continues to form ; filter and test the filtrate for 
acids. 



QUALITATIVE ANALYSIS 259 

(b) The Substance is Insoluble in Water. 3. If the sub- 
stance contains metals of the third, fourth, or fifth group, 
boil some of the solid with a strong solution of sodium 
carbonate for ten minutes, replacing the water which 
evaporates. Filter ; acidify one portion with sulfuric acid, 
boil to expel carbon dioxid, and test for nitric acid; boil 
as before and test as in §§ 370, 371. 

4. If a metal precipitated by hydrogen sulfid is present, 
suspend the substance in water, and pass hydrogen sulfid 
through the solution as long as a precipitate forms. Boil 
a short time; filter, expel hydrogen sulfid, and test the 
filtrate for acids. 

369. Suggestions. — 1. To the solid under examination or 
a concentrated solution, in a small test tube, add a few drops 
of strong sulfuric acid. 

2. Sudden effervescence indicates a carbonate. 

3. Slight effervescence indicates an oxalate. 

4. Odor of hydrogen sulfid indicates a sulfid. 

5. Odor of vinegar indicates an acetate. 

6. Odor of burning matches indicates a sulfite. 

7. Violet vapor indicates an iodid. 

8. Yellow vapor indicates a bromid. 

9. White cloud with ammonium hydroxid indicates a 
chlorid. 

370. For Sulfuric Acid. — To a portion of the original 
solution add barium chlorid. A white precipitate insoluble 
in dilute hydrochloric acid proves the presence of a sulfate. 

371. For Hydrochloric Acid. — To the original solution 
add a few drops of silver nitrate solution ; a white precipi- 
tate insoluble in nitric acid, but soluble in ammonium 
hydroxid, indicates a chlorid. 



260 CHEMISTRY 

372. For Nitric Acid. — Pour a cubic centimetre of strong 
sulfuric acid into a test tube, add an equal volume of the 
solution to be tested; when cool pour a concentrated solu- 
tion of ferrous sulfate carefully down the sides of the tube. 
A brown ring where the two liquids meet indicates nitric 
acid. 

373. For Carbonic Acid. — Treat a concentrated solution 
of the original substance with hydrochloric acid; if effer- 
vescence occurs, hold a drop of barium hydrate on the end 
of a glass rod just above the surface of the liquid ; if it 
becomes turbid, carbonic acid is indicated. 



INDEX 



N. B. The numbers refer to the numbered paragraphs. 



Acetylene, 300-302. 
Acid, acetic, 303. 

arsenious, 337. 

carbonic, 279. 

chloric, 130. 

hydrazoic, 90, 106. 

hydriodic, 115. 

hydrobromic, 139. 

hydrochloric, 122, 311, 345, 371. 

hydrofluoric, 150. 

hydrosulfuric, 106, 168. 

hypochlorous, 130. 

hypophosphorous, 329. 

metaphosphoric, 329. 

muriatic, 122. 

nitric, 98-103. 

orthophosphoric, 329, 330. 

palmitic, 303. 

perchloric, 130. 

phosphoric, 329, 330. 

phosphorus, 329. 

propionic, 303. 

pyrophosphoric, 329. 

stearic, 303. 

sulfuric, 171-76, 341, 370. 
Acid, term defined, 105. 

forming oxids, 104. 

reaction, 70. 

salts, 177. 
Acids, bases and salts, Chap. XII. 

basicity of, 177. 

binary, 106. 

characteristics of, 106. 

classification of, 177. 

fatty, series of, 303. 

names of, 107. 

organic, 303. 

tests for, 368-73. 



Air, analysis of, 30, 31. 

a mixture, 33. 

composition, 33. 

effect on flame, 28. 

effect on metals, 23-27. 

purification of, 283. 

reaction with nitrogen dioxid, 
113. 

soluble in -water, 33. 
Alcohol, 303. 

as preservative, 318. 
Alcoholic fermentation, 312. 
Ale, 312. 

Alkali metals, Chap. XVII. 
Alkaline reaction, 70. 
Allotropism defined, 158. 
Allotropism, of arsenic, 355. 

of carbon, 264. 

of oxygen, 332. 

of phosphorus, 331. 

of sulfur, 158. 
Alloys, 224, 228, 237, 254, 335. 
Alum, 238. 
Aluminum, Chap. XXI. 

compounds of, 238. 

occurrence, 234. 

properties, 236. 

reduction, 235. 

silicate, 239-41. 

uses, 237. 
Amalgamation, 216. 
Ammonia, 90-97, 309. 

liquid, 94. 

occurrence, 90. 

preparation, 91, 93. 

properties of, 

solubility of, 96. 

test, 367. 
261 



262 



INDEX 



Ammonia, uses, 97. 

water, 92. 
Ammonium, 96. 

basic properties of, 198. 

carbonate, 201, 314. 

cblorid, 199, 314. 

hydrosulfid, 203, 314. 

hydroxid, 92, 344. 

nitrate, 111-112, 200. 

salts, 198, 203. 

sulfid, 202, 344. 
Analysis, 22. 

qualitative, Chap. XXXII. 
Animal charcoal, 271. 
Animals, growth of, 281. 

life processes of, 282. 
Anthracite, 308. 
Antichlor, 165. 
Antiseptic, 318. 
Apparatus for analysis, 340. 
Aqua fortis, 125. 
Aqua regia, 125. 
Argon, 32. 
Arsenic, Chap. XXXI. 

mirror, 338-39. 

occurrence, 333. 

oxygen compounds, 336. 

preparation, 334. 

properties, 335. 

test, 338. 

white, 337. 
Arsenious oxid, 337. 
Arsin, 338. 
Atom, 2. 

Atomic theory, 19. 
Atomic weights, table of, 20. 
Atomic weights and densities, 181. 
Atoms, number in molecule, 181. 
Avogadro's law, 180. 

deductions from, 181. 

Baking powder, 197. 
Baking soda, 132, 196. 
Base, definition of, 105. 
Bases, characteristics of, 108. 

removal of, 368. 
Basicity of acids, 177. 
Basic oxids, 101. 
Beer, 312. 
Bell metal, 251. 
Bessemer process, 246. 



Bicarbonate, of potash, 190. 

of soda, 19(3. 
Bituminous coal, 308. 
"Black ash," 195. 
"Black lead," 266. 
Blast furnace, 243. 
Bleaching, by chlorid of lime, 118. 

by chlorin, 118, 121. 

by ozone, 332. 

by powder, 210. 

by sulfur dioxid, 165. 
Blende, 225. 
"Blooming," 215. 
Blowpipes, mouth, use of, 291. 

oxidizing flame of, 291. 

oxy hydrogen, 56. 

reducing flame of, 291. 
Blue vitriol, 221. 
Bohemian glass, 212. 
Boneblack, 271. 
Borax bead test, 361. 
Bower-Barff process, 25. 
Brass, 228, 254. 

Bread making, fermentation in, 310, 
312. 

process, 313. 
Brick, 240. 
Brimstone, 155. 
Britannia metal, 254. 
Bromin, 133-39. 

chemical properties, 136. 

occurrence, 133. 

preparation, 134. 

physical properties, 135. 

test, 138. 

uses, 137. 
Bronze, 251. 
Bunsen burner, 28. 

experiments, 109, 110. 
Burning in air, 39. 
Butane, 292. 
Butyric acid, 303. 

Calami n, 225. 
Calcite, 208. 
Calcium, Cbap. XVIII. 

acid carbonate, 77. 

carbonate, 77, 79,308,213. 

chlorid, 209. 

chloro-bypochlorite, 210. 

chloro-hypochlorite uses, 118. 



INDEX 



263 



Calcium, flue-rid, 204. 

hydroxid, 207. 

light, 56. 

occurrence of, 204. 

oxid, 206. 

phosphate, 204. 

preparation and properties, 205. 

sulfate, 79, 204, 211. 
Calomel, 233. 
Caramel, 313. 
Carat, use of term, 224. 
Carbon, Chap. XXV. 

allotropism of, 264. 

amorphous, 267. 

energy of combustion, 288-89. 

in iron, 244-46. 

kindling temperature, 272. 

occurrence, 264. 

product of combustion, 269. 
Carbonates, 189, 195, 201, 208, 225, 
242, 256, 259, 264, 279. 

acid, 190, 196. 

decomposed, 277. 
Carbon dioxid, 276-84. 

chemical properties of, 279. 

decomposition of, 43, 282. 

diffusion of, 283. 

from baking powders, 197. 

from sodium acid carbonate, 132. 

in air, 31, 283. 

in combustion, 280, 288. 

in fermentation, 312-13. 

in plant life, 282. 

in respiration, 283. 

in ventilation, 284. 

liquid, 278. 

occurrence, 276. 

physical properties, 278. 

preparation, 277. 

solid, 278. 

solubility of, 278. 

test for, 277. 
Carbon disulfid, 13, 134, 142, 143. 
Carbon monoxid, 285-87. 

a reducing agent, 287. 

chemical properties, 287. 

combustion of, 285. 

in coal fires, 285. 

physical properties, 286. 

poisoning, 286. 

preparation, 285. 



Carbonic acid, test, 373. 
Cast iron, white, 244. 

gray, 244. 
Caustic potash, 185. 
Caustic soda, 193. 
Cement, hydraulic, 239. 
Cementation process, 246. 
Cerusite, 256. 
Chalk, 208. 
Charcoal, 267-69. 

animal, 271. 

filters, 79, 269. 

properties of, 269. 
Chemical action, 4-12,' 21. 

and detonation, 10. 

and electricity, 11. 

and heat, 7. 

and light, 8. 

and pressure, 9. 

solution aids, 6. 

and trituration, 12. 
Chemical affinity, 21. 

change, 3. 

compounds and m, '",al mix- 

ture, 13. 

energy, 43. 

equations, 21. 

formula?, 15. 

laws, 16, 18, 180. 

purification of water, 79. 

relations, Cbap. XVI. 

symbols, 14. 
Chemistry, definition, 3. 

inorganic, 264. 

organic, 264. 
Chimneys, to extinguish fire in, 

165. 
Chlorates, 131, 188. 
Chloric acid, 130. 
Chlorid of lime, 118, 210. 
Chlorids, 109, 125. 
Chlorin, 117-21. 

affinity for hydrogen, 118. 

affinity for metals, 118. 

chemical properties, 120. 

occurrence, 117. 

oxids, 129. 

preparation, 118. 

physical properties, 119. 

uses, 121. 

water, 118. 



264 



INDEX 



Chlorin oxyacids, 130. 

preparation, 131. 
Chlorin family, Chap. XIV. 

property of, 152. 
Chlorophyll, 282. 
Chrome yellow, 259. 
Cider, 310, 312. 
Cinnahar, 230. 

Clark's process of softening, 80. 
Classification, of acids, 177. 

of oxids, 101. 

of salts, 177. 
Clay, common, 240. 

porcelain, 211. 
Coal, 308. 

anthracite, 308. 

bituminous, 308. 

distillation of, 306. 

gas, 306. 

gas preparation, 306. 

gas purification, 306. 

tar. 
Cobalt sub-group, 360-61. 
Coke, 307. 

" Cold short " iron, 244. 
Combination by volume, 181 (4) . 
Combustible substances, 40. 
Combustion, Chap. V. 

complete and incomplete, 339. 

heat of, 41, 42, 58, 288. 

in hydrogen, 57. 

of carbon, 288. 

of hydrogen, 58-59. 

products of, 40, 58. 

spontaneous, 41. 
Composition, percentage, 89. 

by volume, 181. 

by weight, 85. 
Compost, ammonia from, 309. 
Compound, definition of, 1, 2. 

binary, 44. 
Concussion causes chemical action, 

10. 
Conduction, loss of heat by, 41. 
Cooling flames, effect of, 27<i, 272-7:;. 
Copper, 220-21. 

compounds of, 221. 

sub-group, 355. 
Cream of tartar, 197. 
Creosote, 318. 
Crith, 88. 



Cryolite, 14/3, 235. 
Crystallization of sulfur, 158. 
Crystallization, water of, 64. 

Decay, 317. 

Decomposition of water, 70, 71. 

Definite proportions, law of, 16. 

Deliquescence, 04. 

Density, vapor, 88. 

and atomic weight, 181. 
Detonation and chemical action, 10. 
Dextrin in bread, 313. 
Diamond, 265. 
Diffusion of gases, 283. 
Disinfectants, 121. 

bleaching powder, 118, 210. 

charcoal, 269. 

chlorin, 121. 

ozone, 332. 

sulfur dioxid, 164. 

zinc chlorid, 229. 
Displacement of air, Exp. 58. 
Distillation, 305. 

destructive, Chap. XXVIII. 

dry, 305. 

fractional, 305. 

natural, 81, 308. 

of soft coal, 306. 

of water, 79. 

of wood, 208. Exp. 118. 

simple chemical, 305. 

simple physical, 305. 
Distilled water, 79. 

Earthenware, 240. 

Effervescence in chemical action, 4. 

Effervescent waters, 75. 

Efflorescence. 04. 

Electricity, development of, 4. 

causes chemical action, 11. 
Electrolysis of water. 66. 
Element, definition, 1. 2. 
Elements, metallic, 104. 

non-metallic, 104. 
Endothermic bodies, 4 '•. 
Endothermic reactions, 43. 
Energy, chemical, 4.:. 
Enzymes, 311. 
Equations, chemical, 21. 

volumetric interpretation of, 181. 
Etching on glass, 151. 



INDEX 



265 



Ethene, 297-99. 

occurrence, 297. 

preparation, 298. 

properties, 299. 
Etherial salts, 303. 
Ethers, 303. 
Ethine, 300-302. 

preparation, 301. 

properties, 302. 
Ethylene, 297-99. 
Eudiometer tube, 67. 
Exothermic bodies, 43. 
Exothermic reactions, 43. 
Expansion by heat, 4. 
Explosion of hydrogen and oxygen, 

50, 67. 
Explosion of hydrogen and chlorin, 

123. 
Explosion in coal mines, 296. 

Factors, 21. 

volumes of, 181. 
Fats, 303. 

saponification of, 304. 
Fatty acids, series of, 303. 

used in candles, 303. 
Feldspar, 234, 241. 
Fermentation, Chap. XXIX. 

acetous, 315. 

acids formed, 314. 

alcoholic, 312. 

definition, 310. 

prevention, 318. 
Ferments, 311. 
Ferric chlorid, 247. 
Ferric disulfid, 249. 
Ferric oxid, 248. 
Ferric salts, 247. 

salts, test for, 359. 
Ferroso-ferric oxid, 248. 
Ferroso -ferric sulfid, 249. 
Ferrous chlorid, 247. 
Ferrous oxid, 248. 
Ferrous salts, 247. 

salts, test for, 359. 
Ferrous sulfate, 250. 
Ferrous sulfid, 249. 
Filters, 79, 269. 
Filtrates, 346. 
Filtration, 79, 269. 

in analysis, 346. 



Fire damp, 293-96. 
Flames, effect of air, 28. 

effect of cooling, 270, 272, 273. 

luminosity of, 290. 

oxidizing, 291. 

reducing, 291. 

smoky, 273. 

structure, etc., 290-91. 
Flint glass, 212. 
Fluorin, 146-51. 

chemical properties, 149. 

occurrence, 146. 

physical properties, 148. 

preparation, 147. 
Fluorspar, 146. 
Formula?, 15. 

Fractional distillation, 305. 
Friction matches, 161, 325. 
Fuels, are endothermic, 43. 

organic, 275. 
Furnace, blast, 243. 

electric, 235, 266. 

reverberatory, 195, 246, 252. 
Fusion, in analysis, 345. 

Galenite, 256. 
Galvanized iron, 25, 228. 
Gas, illuminating, 306. 

marsh, 293. 

natural, 293-95. 

defiant, 297-99. 

to find weight of, 88. 
Gases. See Avogaclro's law, 180. 
German silver, 228, 254. 
Glass, colored, 152. 

etching, 151. 

manufacture, 212. 
Glazes, 240-41. 
Gluten, 313. 
Glycerin, 304. 
Gold, 222-24. 

alloys of, 224. 

coin, 224, 254. 

occurrence, 222. 

properties, 223. 

reduction, 222. 

uses, 224. 
Graphite, 266. 
Gray cast iron, 244. 
Green vitriol, 250. 
Grouping of the metals, 344= 



266 



INDEX 



Growth, 281. 
Gunpowder, 187. 
Gypsum, 211. 

Halogens, the, 116-52. 
Hard water, 77. 

softening, 80. 
Hartshorn, spirits of, 91. 
Heat, effect of, 5. 

effect on solution, 63. 

evolution in chemical action, 4. 

evolution in comhination, 43. 

latent, 63. 

loss of in comhination, 43. 

of combustion, 42. 
Hematite, 242. 
" Hot short " iron, 244. 
Hydraulic cement, 239. 
Hydrazoic acid, 90, 106. 
Hydriodic acid, 145. 
Hydrobromic acid, 139. 
Hydrocarbons, Chap. XXVII. 

definition, 292. 

derivatives of the, 303. 

marsh gas, series of, 292. 
Hydrochloric acid, 122-28. 

as reagent, 341-45. 

composition, 126. 

manufacture of, 127. 

occurrence, 122. 

preparation, 123. 

properties, 125. 

reactions, 124. 

test for, 371. 

uses, 128. 
Hydrofluoric acid, 150. 

action on glass, 151. 
Hydrogen, Chap. VII. 

chemical properties, 53. 

comparison with oxygen, 54. 

energy of combustion, 56, 57. 

product of its combustion, 58. 

occurrence, 50. 

physical properties, 52. 

precautions, 50. 

preparation, 51. 

unit of weight, 20. 

uses of, 55-56. 

valence of, 178. 
Hydrogen arsenid, 338. 
Hydrogen dioxid, 84. 



Hydrogen dioxid, in salts, 177. 
Hydrogen sodium carbonate, 196. 
Hydrogen sulfid, 166--70. 

an acid, 168. 

as reagent, 344. 

occurrence, 166. 

preparations, 167. 

properties, 168. 

test for, 170. 

uses, 169. 
Hydroxids, 65. 
Hypochlorous acid, 130. 
Hypophosphorous acid, 329. 

Ignition, temperature of, 41. 
Illuminating gas, 306. 
Indelible ink, 218. 
Inorganic chemistry, 264. 
Inorganic substances, 264. 
Instability of organic things, 274. 
Iodin, 140-45. 

chemical properties, 143. 

occurrence, 140. 

physical properties, 142. 

preparation, 141. 

test for, 143. 

uses, 144. 
Iron, Chap. XXII. 

cast, 244. 

compounds of, 247. 

compounds of, with oxvsren, 
248. 

compounds of, with sulfur, 249. 

effect of air on, 24. 

extraction from ores, 243. 

galvanized, 199-228. 

gray cast, 244. 

occurrence of, 242. 

pig, 244. 

puddling of, 245. 

sub-group, 359. 

smelting, 243. 

sulfates, 250. 

ways of protecting, 25. 

white cast, 244. 

wrought, 245. 
Isomeric compounds, 310. 
Isomerism, 337. 

Kaolin, 241. 

Kindling temperature, 41. 



INDEX 



267 



Lampblack, 270. 
Lamp flames, 290. 
Laughing gas, 111. 
Law, of Avogadro, 180. 

of definite proportions, 16. 

of multiple proportion, 18. 
Lead, 256-59. 

chromate, 259. 

compounds, 259. 

occurrence, 256. 

properties, 258. 

reduction of, 257. 

uses, 258. 
Leblanc process, 195. 
Life processes, 282. 
Light, in chemical action, 8. 
Lime. See Calcium. 
Litmus, 70. 
Luminosity of flames, 290. 

Marsh gas, 293. 

Marsh's test for arsenic, 338. 

Matches, " parlor," 325. 

safety, 325. 

sulfur, 161. 
Matter, conservation of, 5. 

constitution of, 2. 
Mercury, 230-33. 

alloys of, 231. 

compounds, 233. 

is monatomic, 181. 

occurrence, 230. 

preparation, 230. 

properties, 231. 

rust, 27. 

uses, 232. 
Meta-arsenites, 337. 
Metal, 105. 

bell, 254. 

•Britannia, 254. 
Metals, the alkali, Chap. XVII. 

effect of air on, 23-27. 

decompose water, 70. 

grouping by reagents, 344. 
Metals, qualitative, analysis 
Chap. XXXII. 
First group, 349-51. 
analysis of, 351. 
precipitation of, 349. 
separation of, 350. 
Second group, 352-56. 



of, 



Metals : 
Second group, 
precipitation of, 352. 
sub-groups, 353, 354. 
separation of copper sub-group, 

355. 
separation of tin sub-group, 356. 
Third group, 357-63. 
precipitation, iron sub-group, 

358. 
separation, iron sub-group, 359. 
precipitation, cobalt sub-group, 

360. 
separation, cobalt sub-group, 

361. 
precipitation, presence of phos- 
phates, 362. 
separation, presence of phos- 
phates, 363. 
Fourth group, 364-67. 
precipitation, 364. 
separation, 365. 
Fifth group, 366-67. 
Metalloids, 335. 
Metaphosphoric acid, 329. 
Metathesis, 22. 
Methane, 293-96. 
in coal mines, 296. 
occurrence, 293. 
preparation, 294. 
properties, 294. 
uses, 295. 
Microcrith, 20. 
Microcosmic salt, 330. 
Molecular weight, 85. 

relation to vapor density, 181. 
Molecule, definition, 2. 

relation to atom, 181. 
Mortar, 213. 
Mosaic gold, 255. 
Mouth blowpipe, 291. 

Nascent state, 179. 
Natural gas, 293-95. 
Nessler's test, 82. 
Nitre pots, 174. 
Nitric acid, 98-103. 

chemical properties, 102. 

occurrence, 98. 

physical properties, 101. 

preparation, 99. 



268 



INDEX 



Nitric acid, reaction, 100. 

as reagent, 341, 345. 

test for, 372. 

uses, 103, 172, 173. 
Nitric oxid, 113, 115. 
Nitrogen, Chap. VI. 

in air, 30, 33. 

chemical properties, 49. 

occurrence, 46. 

physical properties, 48» 

preparation, 47. 
Nitrogen dioxid, 113. 
Nitrogen monoxid, 111-12. 
Nitrogen peroxid (tetroxid), 114- 

15. 
Nitroglycerin, 46, 49. 
Nomenclature, of acids, 107. 

of oxids, 44. 

of salts, 109. 
Non-metallic elements, 104. 
Non-metallic oxids, 104. 
Normal salts, 177. 

Normal temperature and pressure, 
88. 



Olefiant gas, 297-99. 
Organic chemistry, 264. 
Organic substances, 264. 
Organic substances as fuels, 275. 
Organic substances unstable, 274. 
Ortho-arsenites, 337. 
Orthophosphoric acid, 329. 
Oxidation, 73. 

in rust, 26. 

of fuels, 43. 
Oxids, metallic and non-metallic, 
104. 

nomenclature, 44. 

occurrence of, 45. 

of nitrogen, 110-15. 

of phosphorus, 326-28. 
Oxygen, Chap. IV. 

chemical properties, 37. 

effect on combustion, 39, 40, 43. 

in air, 27. 

occurrence of, 35. 

physical properties, 36. 

preparation of, 34. 

test for, 34. 

uses, 38. 



Oxy hydrogen blowpipe, 56. 
Ozone, 331-32. 

Palmitic acid, 303. 

Paris green, 337. 

Pattinson process, 216. 

Pearl-ash, 189. 

Peat, 308. 

Pepsin, 311. 

Percentage composition, 89. 

Perchloric acid, 130. 

Perry, 312. 

Phosphates, acid, 330. 

double, 330. 

normal, 330. 

primary, 330. 

precipitation in third group, 362. 

separation in third group, 363. 

test for, 357. 
Phosphorescence, 322. 
Phosphoric acid, 329-30. 

metaphosphoric acid, 329. 

pyrophosphoric acid, 329. 

orthophosphoric acid, 329. 

tribasic acid, 330. 
Phosphorus, Chap. XXX. 

acid, 329. 

allotropism of, 331. 

chemical properties, 322. 

in iron, 244. 

occurrence, 319. 

oxids, 326-28. 

oxyacids, 329. 

pentoxid, 328. 

physical properties, 321. 

preparation, 320. 

red, 323-24. 

solution of, 321. 

trioxid, 327. 

uses, 325. 

vapor density of, 181. 
Photography, 219. 
Pbysical change, 3. 
Pig iron, 243-44. 

varieties of, 244. 
Plants, life processes, 282. 
Plaster of paris, I'll. 
Plastering, hardening of, 213. 
Platinic chlorid, 367. 
Platinum, Chap. XXIV. 

occurrence, 260. 



INDEX 



269 



Platinum, preparation, 261. 

properties, 262. 

uses, 263. 
Plumbago (graphite), 266. 
Polymerism, 337. 
Porcelain, 241. 
Porosity, effect on fuels, 41. 
Potash, 189. 
Potassium, 182-90. 

acid carbonate, 190. 

alum, 238. 

carbonate, 189. 

chlorate, 188. 

hydroxid, 185. 

occurrence, 183. 

preparation, 184. 

properties, 184. 
Potassium nitrate, 186. 
Precipitates, 343. 

washing of, 347. 
Preservation agents, 318. 
Pressure in chemical action, 9. 
Product, 21. 

volume of, 181. 
Proportion, constant laws of, 17. 

multiple laws of, 19. 
"Puddling," 245. 
Purification, of air, 283. 

of water, 79-81. 
Putrefaction, 317. 
Pyro-arsenites, 337. 
Pyrogallic acid, 30. 
Pyrophosphoric acid, 329. 

Qualitative analysis, Chap. XXXII. 
Quantivalence, 178. 
Quicklime, 206. 
Quicksilver, 231. 

Radicals, 96. 
Reaction, 16. 

acid, 70. 

alkaline, 70. 
Reagents, 16. 

in qualitative analysis, 341. 
Realgar, 333. 
Reducing agent, 73. 
Reducing flame, 291. 
Reduction, 73. 
Reverberatory furnace, 245. 
Rouge, jewellers', 248. 



Ruby, 234. 

Rust, formation of, 23, 27. 
effect of, on weight, 26. 

Safety lamps, 41, 296. 
Safety matches, 325. . 
Sal ammoniac, 199. 
Saleratus, 190. 
Salt, common, 194. 
Saltpetre, 98, 140, 186. 
Salts, acid, 177. 

definition, 105. 

naming, 109. 
Salts, normal, 177. 

of radicals, 303. 
Sand filters, 79. 
Saponification, 304. 
Sapphire, 234. 
Scheele's green, 338. 
Schweinfurt green, 338. 
Sedimentation, 81. 
Series, acetylene, 292. 

ethylene, 292. 

marsh gas, 292. 
Shot, arsenic in, 335. 

silicates, 240-tl. 
Silicates in glass, 212. 
Silver, 214-19. 

coin, 254. 

extraction from ores, 216. 

in photography, 219. 

nitrate, 218. 

occurrence, 214. 

properties, 215. 

separation of, from lead, 216. 

uses, 217. 
Slag, 243. 

" Smelling salts," 201. 
Soap, 301. 
Soda, 196. 

baking, 196. 

bicarbonate of, 196. 

caustic, 193. 

washing, 195. 
Soda-ash, 195. 
Soda water, 278. 
Sodium, 191-96. 

acid carbonate, 196. 

as reagent, 341. 

bicarbonate, 196. 

carbonate, 195, 



270 



INDEX 



Sodium, chlorid, 194. 

hydroxid, 193. 

nitrate, 140. 

occurrence, 191. 

preparation, 192. 

properties, 192. 
Solder, 254. 

Soldering, use of ammonia, chlorid 
in, 199. 

use of zinc, chlorid in, 229. 
Solution, chemical, 62. 

definition, 62. 

effect of, 5. 
Solution, effect of heat on, 63. 

physical, 62. 

saturated, 62. 
Solutions, how prepared, 340. 
Solvay process, 195. 
Specific gravity, 88. 

standard of, 61. 
Specific gravity of fuels, 41. 
Specific heat, standard, 61. 
Spontaneous combustion, 41-A2. 
Springs, mineral, 75. 
Stalactites, 279. 
Starch, blue by iodin, 143. 
State, change of, 4. 

nascent, 179. 
Stearic acid, 303. 
Steel, 246. 
Stove polish, 266. 
Structure of flames, 290. 
Sub-groups, 353-61. 
Sulfates, 250. 
Sulfids, test for, 170. 
Sulfur, Chap. XV. 

allotropism of, 158. 

amorphous, 158. 

behavior when heated, 157. 

crystallization of, 158. 

extraction of, 154. 

" flowers " of, 155. 

kindling temperature of, 41, 161. 

matches, 161. 

milk of, 156. 

occurrence of, 153. 

properties of, 159. 

refining of, 155. 

uses of, 160. 
Sulfur dioxid, 162-65. 

occurrence, 162. 



Sulfur dioxid, preparation, 163. 

properties, 164. 

uses, 165. 
Sulfuric acid, 171-76. 

as reagent, 341. 

manufacture of, 174. 

occurrence, 171. 

preparation of, 172. 

properties, 175. 

reactions in, 173. 

test for, 370. 

uses of, 176. 
Supporters of combustion, 37, 57. 
Symbols, 14. 
Sympathetic ink, 64. 
Synthesis, 22. 

Temperature, kindling, 41. 
Temperatures, standard, 61. 
Terminations ous and ic, 44, 107. 
Terne plate, 253. 
Thermal relations of chemical 

changes, 43. 
Tile, 240. 
Tin, 251-55. 

alloys of, 254. 

compounds, 255. 

occurrence, 251. 

plate, 253. 

properties, 253. 

reduction, 252. 

sub-group (analysis) , 356. 
Tinned iron, 253. 
Tin salts, 255. 
Travertine, 279. 
Trituration in chemical action, 12. 

Valence, theory of, 178. 
Vapor density, 88. 

table, 181. 
Ventilation, 284. 
Vinegar, 316. 

" mother of," 316. 

prevent fermentation, 318. 
Vitriol, blue, 221. 

green, 250. 

oil of, 171-76. 
Volume, change of, 4. 

relation to density, ISO. 

relation to molecular weight, 1*1. 
Volumetric relations, 181. 



INDEX 



271 



"Washing soda, 195. 
Water, analysis of, 66. 

as a solvent, 02-63. 

by hot oxid process, 68. 

chemistry of, Chap. Tin. 

composition of, 66, 69. 

decomposed by electricity, 70. 

decomposed by metals, 70-71. 

dissolves air, 33. 

distilled, 79. 

effervescent, 75. 

electrolysis of, 66. 

formed by combustion, 59. 

hard, 77. 

hov^ removed, 79. 

impurities in, 74. 

in analysis, 315. 

mineral, 71-75. 

occurrence, 60. 

of crystallization, 61. 

organic impurities in, 82. 

potable, 78. 

properties, 61. 

purification of, 79, 81. 

purity of natural, 71. 

river, 76. 

soda, 278. 

softening, 80. 

spring, 75. 

standard of specific gravity, 61. 

standard of specific heat, 61. 



Water, synthesis of, 67= 

temperatures of, 61. 

tests for impurities, 82-83. 
Water gas, 72. 
Waters, effervescent, 75. 

chalybeate, 75. 

natural, 71. 

sulfur, 75. 
Weight, composition by, 85-87. 

loss of, by combustion, 29. 

of gas, 88. 
Weights, atomic, 20. 

combining, 17. 
Wet process of analysis, 3H-73. 
Whiskey, 312. 
White arsenic, 337. 
White cast iron, 211. 
White lead, 259. 
Wines, 312. 
Wire gauze, 11, 199. 
Wood, distillation of, 268, 306. 
Wrought iron, 215. 

Zinc, 225-29. 

action of acids on, 50. 
alloys of, 228, 251. 
compounds of, 229. 
occurrence, 225. 
preparation, 226. 
properties, 227. 
uses, 228. 



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